diff --git a/Cargo.lock b/Cargo.lock
index d4114eff1f..5ec9c48524 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -397,6 +397,7 @@ dependencies = [
  "boa_macros",
  "boa_parser",
  "boa_profiler",
+ "boa_types",
  "bytemuck",
  "cfg-if",
  "chrono",
@@ -585,6 +586,21 @@ dependencies = [
  "toml 0.8.6",
 ]
 
+[[package]]
+name = "boa_types"
+version = "0.17.0"
+dependencies = [
+ "boa_gc",
+ "boa_macros",
+ "fast-float",
+ "num_enum",
+ "paste",
+ "phf",
+ "portable-atomic",
+ "sptr",
+ "static_assertions",
+]
+
 [[package]]
 name = "boa_wasm"
 version = "0.17.0"
diff --git a/Cargo.toml b/Cargo.toml
index 9028f2dc9b..421e494c24 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,6 +7,7 @@ members = [
     "boa_examples",
     "boa_gc",
     "boa_icu_provider",
+    "boa_types",
     "boa_interner",
     "boa_macros",
     "boa_macros_tests",
@@ -33,6 +34,7 @@ boa_ast = { version = "~0.17.0", path = "boa_ast" }
 boa_engine = { version = "~0.17.0", path = "boa_engine" }
 boa_gc = { version = "~0.17.0", path = "boa_gc" }
 boa_icu_provider = { version = "~0.17.0", path = "boa_icu_provider" }
+boa_types = { version = "~0.17.0", path = "boa_types" }
 boa_interner = { version = "~0.17.0", path = "boa_interner" }
 boa_macros = { version = "~0.17.0", path = "boa_macros" }
 boa_parser = { version = "~0.17.0", path = "boa_parser" }
diff --git a/boa_engine/Cargo.toml b/boa_engine/Cargo.toml
index f6384439c9..1ab62b733a 100644
--- a/boa_engine/Cargo.toml
+++ b/boa_engine/Cargo.toml
@@ -62,6 +62,7 @@ boa_profiler.workspace = true
 boa_macros.workspace = true
 boa_ast.workspace = true
 boa_parser.workspace = true
+boa_types.workspace = true
 serde = { workspace = true, features = ["derive", "rc"] }
 serde_json.workspace = true
 rand = "0.8.5"
diff --git a/boa_engine/src/bigint.rs b/boa_engine/src/bigint.rs
index 80b3691ed1..3ee13c7893 100644
--- a/boa_engine/src/bigint.rs
+++ b/boa_engine/src/bigint.rs
@@ -1,6 +1,6 @@
 //! Boa's implementation of ECMAScript's bigint primitive type.
 
-use crate::{builtins::Number, error::JsNativeError, JsResult};
+use crate::{builtins::Number, error::JsNativeError, JsResult, JsString};
 use num_integer::Integer;
 use num_traits::{pow::Pow, FromPrimitive, One, ToPrimitive, Zero};
 use std::{
@@ -86,6 +86,22 @@ impl JsBigInt {
         })
     }
 
+    /// Abstract operation `StringToBigInt ( str )`
+    ///
+    /// More information:
+    /// - [ECMAScript reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-stringtobigint
+    pub(crate) fn from_js_string(string: &JsString) -> Option<JsBigInt> {
+        // 1. Let text be ! StringToCodePoints(str).
+        // 2. Let literal be ParseText(text, StringIntegerLiteral).
+        // 3. If literal is a List of errors, return undefined.
+        // 4. Let mv be the MV of literal.
+        // 5. Assert: mv is an integer.
+        // 6. Return ℤ(mv).
+        JsBigInt::from_string(string.to_std_string().ok().as_ref()?)
+    }
+
     /// This function takes a string and converts it to `BigInt` type.
     ///
     /// More information:
diff --git a/boa_engine/src/builtins/function/mod.rs b/boa_engine/src/builtins/function/mod.rs
index 55aa645c93..693d9ea2c8 100644
--- a/boa_engine/src/builtins/function/mod.rs
+++ b/boa_engine/src/builtins/function/mod.rs
@@ -22,7 +22,7 @@ use crate::{
     object::{JsFunction, PrivateElement, PrivateName},
     property::{Attribute, PropertyDescriptor, PropertyKey},
     realm::Realm,
-    string::{common::StaticJsStrings, utf16},
+    string::common::StaticJsStrings,
     symbol::JsSymbol,
     value::IntegerOrInfinity,
     vm::{ActiveRunnable, CodeBlock},
@@ -37,6 +37,7 @@ use boa_ast::{
 };
 use boa_gc::{self, custom_trace, Finalize, Gc, Trace};
 use boa_interner::Sym;
+use boa_macros::utf16;
 use boa_parser::{Parser, Source};
 use boa_profiler::Profiler;
 use std::io::Read;
diff --git a/boa_engine/src/builtins/json/mod.rs b/boa_engine/src/builtins/json/mod.rs
index 524b4e1ba7..ebbaffa3b0 100644
--- a/boa_engine/src/builtins/json/mod.rs
+++ b/boa_engine/src/builtins/json/mod.rs
@@ -15,6 +15,7 @@
 
 use std::{borrow::Cow, iter::once};
 
+use boa_macros::utf16;
 use itertools::Itertools;
 
 use crate::{
@@ -26,7 +27,7 @@ use crate::{
     object::JsObject,
     property::{Attribute, PropertyNameKind},
     realm::Realm,
-    string::{common::StaticJsStrings, utf16, CodePoint},
+    string::{common::StaticJsStrings, CodePoint},
     symbol::JsSymbol,
     value::IntegerOrInfinity,
     vm::{CallFrame, CallFrameFlags},
diff --git a/boa_engine/src/builtins/regexp/mod.rs b/boa_engine/src/builtins/regexp/mod.rs
index fafeea5f8c..aa0d4a9b2a 100644
--- a/boa_engine/src/builtins/regexp/mod.rs
+++ b/boa_engine/src/builtins/regexp/mod.rs
@@ -19,11 +19,12 @@ use crate::{
     },
     property::Attribute,
     realm::Realm,
-    string::{common::StaticJsStrings, utf16, CodePoint},
+    string::{common::StaticJsStrings, CodePoint},
     symbol::JsSymbol,
     value::JsValue,
     Context, JsArgs, JsResult, JsString,
 };
+use boa_macros::utf16;
 use boa_parser::lexer::regex::RegExpFlags;
 use boa_profiler::Profiler;
 use regress::{Flags, Range, Regex};
diff --git a/boa_engine/src/builtins/string/mod.rs b/boa_engine/src/builtins/string/mod.rs
index e47bec6c34..833c240969 100644
--- a/boa_engine/src/builtins/string/mod.rs
+++ b/boa_engine/src/builtins/string/mod.rs
@@ -17,12 +17,13 @@ use crate::{
     object::{internal_methods::get_prototype_from_constructor, JsObject, ObjectData},
     property::{Attribute, PropertyDescriptor},
     realm::Realm,
+    string::common::StaticJsStrings,
     string::CodePoint,
-    string::{common::StaticJsStrings, utf16},
     symbol::JsSymbol,
     value::IntegerOrInfinity,
     Context, JsArgs, JsResult, JsString, JsValue,
 };
+use boa_macros::utf16;
 use boa_profiler::Profiler;
 use icu_normalizer::{ComposingNormalizer, DecomposingNormalizer};
 use std::cmp::{max, min};
diff --git a/boa_engine/src/lib.rs b/boa_engine/src/lib.rs
index 0fee87c626..ae33df731d 100644
--- a/boa_engine/src/lib.rs
+++ b/boa_engine/src/lib.rs
@@ -128,8 +128,6 @@
 #[cfg(not(target_has_atomic = "ptr"))]
 compile_error!("Boa requires a lock free `AtomicUsize` in order to work properly.");
 
-extern crate static_assertions as sa;
-
 pub mod bigint;
 pub mod builtins;
 pub mod bytecompiler;
@@ -145,15 +143,12 @@ pub mod optimizer;
 pub mod property;
 pub mod realm;
 pub mod script;
-pub mod string;
-pub mod symbol;
 pub mod value;
 pub mod vm;
 
 mod host_defined;
 mod small_map;
 mod sys;
-mod tagged;
 
 #[cfg(test)]
 mod tests;
@@ -184,12 +179,16 @@ pub use crate::{
     native_function::NativeFunction,
     object::JsObject,
     script::Script,
-    string::JsString,
-    symbol::JsSymbol,
     value::JsValue,
 };
 #[doc(inline)]
 pub use boa_parser::Source;
+#[doc(inline)]
+pub use boa_types::{
+    js_string,
+    string::{self, JsString},
+    symbol::{self, JsSymbol},
+};
 
 /// The result of a Javascript expression is represented like this so it can succeed (`Ok`) or fail (`Err`)
 pub type JsResult<T> = StdResult<T, JsError>;
diff --git a/boa_engine/src/value/equality.rs b/boa_engine/src/value/equality.rs
index 7e9255c381..faa8d7e284 100644
--- a/boa_engine/src/value/equality.rs
+++ b/boa_engine/src/value/equality.rs
@@ -65,14 +65,14 @@ impl JsValue {
             //    a. Let n be ! StringToBigInt(y).
             //    b. If n is NaN, return false.
             //    c. Return the result of the comparison x == n.
-            (Self::BigInt(ref a), Self::String(ref b)) => {
-                b.to_big_int().as_ref().map_or(false, |b| a == b)
-            }
+            (Self::BigInt(ref a), Self::String(ref b)) => JsBigInt::from_js_string(b)
+                .as_ref()
+                .map_or(false, |b| a == b),
 
             // 7. If Type(x) is String and Type(y) is BigInt, return the result of the comparison y == x.
-            (Self::String(ref a), Self::BigInt(ref b)) => {
-                a.to_big_int().as_ref().map_or(false, |a| a == b)
-            }
+            (Self::String(ref a), Self::BigInt(ref b)) => JsBigInt::from_js_string(a)
+                .as_ref()
+                .map_or(false, |a| a == b),
 
             // 8. If Type(x) is Boolean, return the result of the comparison ! ToNumber(x) == y.
             (Self::Boolean(x), _) => return other.equals(&Self::new(i32::from(*x)), context),
diff --git a/boa_engine/src/value/mod.rs b/boa_engine/src/value/mod.rs
index 9bb440d89b..9a414ec9d1 100644
--- a/boa_engine/src/value/mod.rs
+++ b/boa_engine/src/value/mod.rs
@@ -413,7 +413,7 @@ impl JsValue {
             Self::Undefined => Err(JsNativeError::typ()
                 .with_message("cannot convert undefined to a BigInt")
                 .into()),
-            Self::String(ref string) => string.to_big_int().map_or_else(
+            Self::String(ref string) => JsBigInt::from_js_string(string).map_or_else(
                 || {
                     Err(JsNativeError::syntax()
                         .with_message(format!(
diff --git a/boa_engine/src/value/operations.rs b/boa_engine/src/value/operations.rs
index 44fe42b37a..b837e1870c 100644
--- a/boa_engine/src/value/operations.rs
+++ b/boa_engine/src/value/operations.rs
@@ -537,11 +537,9 @@ impl JsValue {
 
                 match (px, py) {
                     (Self::String(ref x), Self::String(ref y)) => (x < y).into(),
-                    (Self::BigInt(ref x), Self::String(ref y)) => y
-                        .to_big_int()
+                    (Self::BigInt(ref x), Self::String(ref y)) => JsBigInt::from_js_string(y)
                         .map_or(AbstractRelation::Undefined, |y| (*x < y).into()),
-                    (Self::String(ref x), Self::BigInt(ref y)) => x
-                        .to_big_int()
+                    (Self::String(ref x), Self::BigInt(ref y)) => JsBigInt::from_js_string(x)
                         .map_or(AbstractRelation::Undefined, |x| (x < *y).into()),
                     (px, py) => match (px.to_numeric(context)?, py.to_numeric(context)?) {
                         (Numeric::Number(x), Numeric::Number(y)) => Number::less_than(x, y),
diff --git a/boa_types/ABOUT.md b/boa_types/ABOUT.md
new file mode 100644
index 0000000000..0deb7c9a49
--- /dev/null
+++ b/boa_types/ABOUT.md
@@ -0,0 +1,33 @@
+# About Boa
+
+Boa is an open-source, experimental ECMAScript Engine written in Rust for
+lexing, parsing and executing ECMAScript/JavaScript. Currently, Boa supports some
+of the [language][boa-conformance]. More information can be viewed at [Boa's
+website][boa-web].
+
+Try out the most recent release with Boa's live demo
+[playground][boa-playground].
+
+# Boa Crates
+
+- [**`boa_ast`**][ast] - Boa's ECMAScript Abstract Syntax Tree.
+- [**`boa_engine`**][engine] - Boa's implementation of ECMAScript builtin objects and
+  execution.
+- [**`boa_gc`**][gc] - Boa's garbage collector.
+- [**`boa_interner`**][interner] - Boa's string interner.
+- [**`boa_parser`**][parser] - Boa's lexer and parser.
+- [**`boa_profiler`**][profiler] - Boa's code profiler.
+- [**`boa_icu_provider`**][icu] - Boa's ICU4X data provider.
+- [**`boa_runtime`**][runtime] - Boa's WebAPI features.
+
+[boa-conformance]: https://boajs.dev/boa/test262/
+[boa-web]: https://boajs.dev/
+[boa-playground]: https://boajs.dev/boa/playground/
+[ast]: https://boajs.dev/boa/doc/boa_ast/index.html
+[engine]: https://boajs.dev/boa/doc/boa_engine/index.html
+[gc]: https://boajs.dev/boa/doc/boa_gc/index.html
+[interner]: https://boajs.dev/boa/doc/boa_interner/index.html
+[parser]: https://boajs.dev/boa/doc/boa_parser/index.html
+[profiler]: https://boajs.dev/boa/doc/boa_profiler/index.html
+[icu]: https://boajs.dev/boa/doc/boa_icu_provider/index.html
+[runtime]: https://boajs.dev/boa/doc/boa_runtime/index.html
diff --git a/boa_types/Cargo.toml b/boa_types/Cargo.toml
new file mode 100644
index 0000000000..9604c38a2f
--- /dev/null
+++ b/boa_types/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "boa_types"
+description = "String for the Boa JavaScript engine."
+keywords = ["javascript", "js", "string"]
+categories = ["data-structures", "no-std"]
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+boa_gc.workspace = true
+fast-float.workspace = true
+sptr = "0.3.2"
+static_assertions.workspace = true
+num_enum = "0.7.0"
+paste = "1.0"
+portable-atomic = "1.5.0"
+phf.workspace = true
+
+[dev-dependencies]
+boa_macros.workspace = true
diff --git a/boa_types/src/lib.rs b/boa_types/src/lib.rs
new file mode 100644
index 0000000000..5fa18bd524
--- /dev/null
+++ b/boa_types/src/lib.rs
@@ -0,0 +1,100 @@
+//! Boa's **`boa_interner`** is a string interner for compiler performance.
+//!
+//! # Crate Overview
+//!
+//! The idea behind using a string interner is that in most of the code, strings such as
+//! identifiers and literals are often repeated. This causes extra burden when comparing them and
+//! storing them. A string interner stores a unique `usize` symbol for each string, making sure
+//! that there are no duplicates. This makes it much easier to compare, since it's just comparing
+//! to `usize`, and also it's easier to store, since instead of a heap-allocated string, you only
+//! need to store a `usize`. This reduces memory consumption and improves performance in the
+//! compiler.
+#![doc = include_str!("../ABOUT.md")]
+#![doc(
+    html_logo_url = "https://raw.githubusercontent.com/boa-dev/boa/main/assets/logo.svg",
+    html_favicon_url = "https://raw.githubusercontent.com/boa-dev/boa/main/assets/logo.svg"
+)]
+#![cfg_attr(not(test), forbid(clippy::unwrap_used))]
+#![warn(
+    // rustc lint groups https://doc.rust-lang.org/rustc/lints/groups.html
+    warnings,
+    future_incompatible,
+    let_underscore,
+    nonstandard_style,
+    rust_2018_compatibility,
+    rust_2018_idioms,
+    rust_2021_compatibility,
+    unused,
+
+    // rustc allowed-by-default lints https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default.html
+    missing_docs,
+    macro_use_extern_crate,
+    meta_variable_misuse,
+    missing_abi,
+    missing_copy_implementations,
+    missing_debug_implementations,
+    non_ascii_idents,
+    noop_method_call,
+    single_use_lifetimes,
+    trivial_casts,
+    trivial_numeric_casts,
+    unreachable_pub,
+    unsafe_op_in_unsafe_fn,
+    unused_crate_dependencies,
+    unused_import_braces,
+    unused_lifetimes,
+    unused_qualifications,
+    unused_tuple_struct_fields,
+    variant_size_differences,
+
+    // rustdoc lints https://doc.rust-lang.org/rustdoc/lints.html
+    rustdoc::broken_intra_doc_links,
+    rustdoc::private_intra_doc_links,
+    rustdoc::missing_crate_level_docs,
+    rustdoc::private_doc_tests,
+    rustdoc::invalid_codeblock_attributes,
+    rustdoc::invalid_rust_codeblocks,
+    rustdoc::bare_urls,
+
+    // clippy allowed by default
+    clippy::dbg_macro,
+
+    // clippy categories https://doc.rust-lang.org/clippy/
+    clippy::all,
+    clippy::correctness,
+    clippy::suspicious,
+    clippy::style,
+    clippy::complexity,
+    clippy::perf,
+    clippy::pedantic,
+)]
+#![allow(
+    clippy::redundant_pub_crate,
+    // TODO deny once false positive is fixed (https://github.com/rust-lang/rust-clippy/issues/9626).
+    clippy::trait_duplication_in_bounds
+)]
+
+/// Helper function to check if a `char` is trimmable.
+#[must_use]
+pub const fn is_trimmable_whitespace(c: char) -> bool {
+    // The rust implementation of `trim` does not regard the same characters whitespace as ecma standard does
+    //
+    // Rust uses \p{White_Space} by default, which also includes:
+    // `\u{0085}' (next line)
+    // And does not include:
+    // '\u{FEFF}' (zero width non-breaking space)
+    // Explicit whitespace: https://tc39.es/ecma262/#sec-white-space
+    matches!(
+        c,
+        '\u{0009}' | '\u{000B}' | '\u{000C}' | '\u{0020}' | '\u{00A0}' | '\u{FEFF}' |
+    // Unicode Space_Separator category
+    '\u{1680}' | '\u{2000}'
+            ..='\u{200A}' | '\u{202F}' | '\u{205F}' | '\u{3000}' |
+    // Line terminators: https://tc39.es/ecma262/#sec-line-terminators
+    '\u{000A}' | '\u{000D}' | '\u{2028}' | '\u{2029}'
+    )
+}
+
+pub mod string;
+pub mod symbol;
+pub(crate) mod tagged;
diff --git a/boa_engine/src/string/common.rs b/boa_types/src/string/common.rs
similarity index 99%
rename from boa_engine/src/string/common.rs
rename to boa_types/src/string/common.rs
index b98481b70a..5f8e0c884a 100644
--- a/boa_engine/src/string/common.rs
+++ b/boa_types/src/string/common.rs
@@ -1,3 +1,5 @@
+//! List of commonly used strings in Javascript code.
+
 use crate::tagged::Tagged;
 
 use super::JsString;
@@ -8,8 +10,7 @@ macro_rules! well_known_statics {
         $(
             paste!{
                 #[doc = "Gets the static `JsString` for `\"" $string "\"`."]
-                #[allow(unused)]
-                pub(crate) const $name: JsString = JsString {
+                pub const $name: JsString = JsString {
                     ptr: Tagged::from_tag(
                         Self::find_index($string),
                     ),
@@ -22,8 +23,8 @@ macro_rules! well_known_statics {
 /// List of commonly used strings in Javascript code.
 ///
 /// Any strings defined here are used as a static [`JsString`] instead of allocating on the heap.
-#[derive(Debug)]
-pub(crate) struct StaticJsStrings;
+#[derive(Debug, Clone, Copy)]
+pub struct StaticJsStrings;
 
 impl StaticJsStrings {
     // useful to search at compile time a certain string in the array
diff --git a/boa_engine/src/string/mod.rs b/boa_types/src/string/mod.rs
similarity index 96%
rename from boa_engine/src/string/mod.rs
rename to boa_types/src/string/mod.rs
index 0362478606..582ecc2e5e 100644
--- a/boa_engine/src/string/mod.rs
+++ b/boa_types/src/string/mod.rs
@@ -21,17 +21,12 @@
 // the same names from the unstable functions of the `std::ptr` module.
 #![allow(unstable_name_collisions)]
 
-pub(crate) mod common;
+pub mod common;
 mod slice;
 mod str;
 
-use crate::{
-    builtins::string::is_trimmable_whitespace,
-    tagged::{Tagged, UnwrappedTagged},
-    JsBigInt,
-};
+use crate::tagged::{Tagged, UnwrappedTagged};
 use boa_gc::{empty_trace, Finalize, Trace};
-pub use boa_macros::utf16;
 
 #[doc(inline)]
 pub use crate::string::{
@@ -64,7 +59,6 @@ fn alloc_overflow() -> ! {
 ///
 /// ```
 /// use boa_engine::js_string;
-/// use boa_engine::string::utf16;
 ///
 /// let empty_str = js_string!();
 /// assert!(empty_str.is_empty());
@@ -76,7 +70,6 @@ fn alloc_overflow() -> ! {
 ///
 /// ```
 /// # use boa_engine::js_string;
-/// # use boa_engine::string::utf16;
 /// let hw = js_string!("Hello, world!");
 /// assert_eq!(&hw, "Hello, world!");
 /// ```
@@ -93,7 +86,6 @@ fn alloc_overflow() -> ! {
 ///
 /// ```
 /// # use boa_engine::js_string;
-/// # use boa_engine::string::utf16;
 /// const NAME: &[u16] = "human! ";
 /// let greeting = js_string!("Hello, ");
 /// let msg = js_string!(&greeting, &NAME, "Nice to meet you!");
@@ -101,21 +93,22 @@ fn alloc_overflow() -> ! {
 /// assert_eq!(&msg, "Hello, human! Nice to meet you!");
 /// ```
 #[macro_export]
+#[allow(clippy::module_name_repetitions)]
 macro_rules! js_string {
     () => {
-        $crate::JsString::default()
+        $crate::string::JsString::default()
     };
     ($s:literal) => {
-        $crate::JsString::from($s)
+        $crate::string::JsString::from($s)
     };
     ($s:expr) => {
-        $crate::JsString::from($s)
+        $crate::string::JsString::from($s)
     };
     ( $x:expr, $y:expr ) => {
-        $crate::JsString::concat($crate::string::JsStringSlice::from($x), $crate::string::JsStringSlice::from($y))
+        $crate::string::JsString::concat($crate::string::JsStringSlice::from($x), $crate::string::JsStringSlice::from($y))
     };
     ( $( $s:expr ),+ ) => {
-        $crate::JsString::concat_array(&[ $( $crate::string::JsStringSlice::from($s) ),+ ])
+        $crate::string::JsString::concat_array(&[ $( $crate::string::JsStringSlice::from($s) ),+ ])
     };
 }
 
@@ -212,12 +205,13 @@ const DATA_OFFSET: usize = std::mem::size_of::<RawJsString>();
 /// [`JsString`] implements <code>[Deref]<Target = \[u16\]></code>, inheriting all of
 /// <code>\[u16\]</code>'s methods.
 #[derive(Finalize)]
+#[allow(clippy::module_name_repetitions)]
 pub struct JsString {
     ptr: Tagged<RawJsString>,
 }
 
 // JsString should always be pointer sized.
-sa::assert_eq_size!(JsString, *const ());
+static_assertions::assert_eq_size!(JsString, *const ());
 
 // Safety: `JsString` does not contain any objects which needs to be traced, so this is safe.
 unsafe impl Trace for JsString {
@@ -435,6 +429,9 @@ impl JsString {
     }
 
     /// Decodes a [`JsString`] into a [`String`], returning
+    ///
+    /// # Errors
+    ///
     /// [`FromUtf16Error`][std::string::FromUtf16Error] if it contains any invalid data.
     pub fn to_std_string(&self) -> Result<String, std::string::FromUtf16Error> {
         match self.as_str().variant() {
@@ -530,7 +527,7 @@ impl JsString {
     ///  - [ECMAScript reference][spec]
     ///
     /// [spec]: https://tc39.es/ecma262/#sec-stringindexof
-    pub(crate) fn index_of(&self, search_value: &JsStr<'_>, from_index: usize) -> Option<usize> {
+    pub fn index_of(&self, search_value: &JsStr<'_>, from_index: usize) -> Option<usize> {
         let this = self.iter().collect::<Vec<_>>();
         let search_value = search_value.iter().collect::<Vec<_>>();
 
@@ -573,7 +570,12 @@ impl JsString {
     ///  - [ECMAScript reference][spec]
     ///
     /// [spec]: https://tc39.es/ecma262/#sec-codepointat
-    pub(crate) fn code_point_at(&self, position: usize) -> CodePoint {
+    ///
+    /// # Panics
+    ///
+    /// If `position` is smaller than size of string.
+    #[must_use]
+    pub fn code_point_at(&self, position: usize) -> CodePoint {
         // 1. Let size be the length of string.
         let size = self.len();
 
@@ -613,7 +615,7 @@ impl JsString {
     /// - [ECMAScript reference][spec]
     ///
     /// [spec]: https://tc39.es/ecma262/#sec-stringtonumber
-    pub(crate) fn to_number(&self) -> f64 {
+    pub fn to_number(&self) -> f64 {
         // 1. Let text be ! StringToCodePoints(str).
         // 2. Let literal be ParseText(text, StringNumericLiteral).
         let Ok(string) = self.to_std_string() else {
@@ -621,7 +623,7 @@ impl JsString {
             return f64::NAN;
         };
         // 4. Return StringNumericValue of literal.
-        let string = string.trim_matches(is_trimmable_whitespace);
+        let string = string.trim_matches(crate::is_trimmable_whitespace);
         match string {
             "" => return 0.0,
             "-Infinity" => return f64::NEG_INFINITY,
@@ -668,22 +670,6 @@ impl JsString {
         fast_float::parse(string).unwrap_or(f64::NAN)
     }
 
-    /// Abstract operation `StringToBigInt ( str )`
-    ///
-    /// More information:
-    /// - [ECMAScript reference][spec]
-    ///
-    /// [spec]: https://tc39.es/ecma262/#sec-stringtobigint
-    pub(crate) fn to_big_int(&self) -> Option<JsBigInt> {
-        // 1. Let text be ! StringToCodePoints(str).
-        // 2. Let literal be ParseText(text, StringIntegerLiteral).
-        // 3. If literal is a List of errors, return undefined.
-        // 4. Let mv be the MV of literal.
-        // 5. Assert: mv is an integer.
-        // 6. Return ℤ(mv).
-        JsBigInt::from_string(self.to_std_string().ok().as_ref()?)
-    }
-
     /// Allocates a new [`RawJsString`] with an internal capacity of `str_len` chars.
     ///
     /// # Panics
@@ -866,15 +852,15 @@ impl JsString {
         }
     }
 
-    pub(crate) fn trim(&self) -> JsStringSlice<'_> {
+    pub fn trim(&self) -> JsStringSlice<'_> {
         self.as_str().trim()
     }
 
-    pub(crate) fn trim_start(&self) -> JsStringSlice<'_> {
+    pub fn trim_start(&self) -> JsStringSlice<'_> {
         self.as_str().trim_start()
     }
 
-    pub(crate) fn trim_end(&self) -> JsStringSlice<'_> {
+    pub fn trim_end(&self) -> JsStringSlice<'_> {
         self.as_str().trim_end()
     }
 
@@ -1172,8 +1158,8 @@ impl ToStringEscaped for [u16] {
 mod tests {
     use crate::tagged::UnwrappedTagged;
 
-    use super::utf16;
     use super::JsString;
+    use boa_macros::utf16;
 
     impl JsString {
         /// Gets the number of `JsString`s which point to this allocation.
diff --git a/boa_engine/src/string/slice.rs b/boa_types/src/string/slice.rs
similarity index 89%
rename from boa_engine/src/string/slice.rs
rename to boa_types/src/string/slice.rs
index e386be9ff3..ac7d88f190 100644
--- a/boa_engine/src/string/slice.rs
+++ b/boa_types/src/string/slice.rs
@@ -1,4 +1,24 @@
-use crate::{builtins::string::is_trimmable_whitespace, JsString};
+use crate::string::JsString;
+
+/// Helper function to check if a `char` is trimmable.
+pub(crate) const fn is_trimmable_whitespace(c: char) -> bool {
+    // The rust implementation of `trim` does not regard the same characters whitespace as ecma standard does
+    //
+    // Rust uses \p{White_Space} by default, which also includes:
+    // `\u{0085}' (next line)
+    // And does not include:
+    // '\u{FEFF}' (zero width non-breaking space)
+    // Explicit whitespace: https://tc39.es/ecma262/#sec-white-space
+    matches!(
+        c,
+        '\u{0009}' | '\u{000B}' | '\u{000C}' | '\u{0020}' | '\u{00A0}' | '\u{FEFF}' |
+    // Unicode Space_Separator category
+    '\u{1680}' | '\u{2000}'
+            ..='\u{200A}' | '\u{202F}' | '\u{205F}' | '\u{3000}' |
+    // Line terminators: https://tc39.es/ecma262/#sec-line-terminators
+    '\u{000A}' | '\u{000D}' | '\u{2028}' | '\u{2029}'
+    )
+}
 
 use super::{is_ascii, JsStr, JsStrVariant};
 
diff --git a/boa_engine/src/string/str.rs b/boa_types/src/string/str.rs
similarity index 94%
rename from boa_engine/src/string/str.rs
rename to boa_types/src/string/str.rs
index 6413c243e2..e62a58470e 100644
--- a/boa_engine/src/string/str.rs
+++ b/boa_types/src/string/str.rs
@@ -1,7 +1,6 @@
 use std::slice::SliceIndex;
 
 use crate::string::Iter;
-use boa_interner::JStrRef;
 
 use super::JsStringSlice;
 
@@ -75,13 +74,6 @@ impl<'a> JsStr<'a> {
         Iter::new(self.into())
     }
 
-    pub(crate) fn as_str_ref(&self) -> JStrRef<'_> {
-        match self.inner {
-            JsStrVariant::Ascii(s) => JStrRef::Utf8(s),
-            JsStrVariant::U16(s) => JStrRef::Utf16(s),
-        }
-    }
-
     #[inline]
     #[must_use]
     pub fn is_empty(&self) -> bool {
diff --git a/boa_engine/src/symbol.rs b/boa_types/src/symbol.rs
similarity index 98%
rename from boa_engine/src/symbol.rs
rename to boa_types/src/symbol.rs
index ce625158c8..afd496e5cd 100644
--- a/boa_engine/src/symbol.rs
+++ b/boa_types/src/symbol.rs
@@ -23,9 +23,8 @@
 
 use crate::{
     js_string,
-    string::common::StaticJsStrings,
+    string::{common::StaticJsStrings, JsString},
     tagged::{Tagged, UnwrappedTagged},
-    JsString,
 };
 use boa_gc::{empty_trace, Finalize, Trace};
 
@@ -131,6 +130,7 @@ struct Inner {
 }
 
 /// This represents a JavaScript symbol primitive.
+#[allow(clippy::module_name_repetitions)]
 pub struct JsSymbol {
     repr: Tagged<Inner>,
 }
@@ -151,7 +151,10 @@ unsafe impl Trace for JsSymbol {
 macro_rules! well_known_symbols {
     ( $( $(#[$attr:meta])* ($name:ident, $variant:path) ),+$(,)? ) => {
         $(
-            $(#[$attr])* pub(crate) const fn $name() -> JsSymbol {
+            $(#[$attr])*
+            #[must_use]
+            #[inline]
+            pub const fn $name() -> JsSymbol {
                 JsSymbol {
                     // the cast shouldn't matter since we only have 127 const symbols
                     repr: Tagged::from_tag($variant.hash() as usize),
diff --git a/boa_engine/src/tagged.rs b/boa_types/src/tagged.rs
similarity index 100%
rename from boa_engine/src/tagged.rs
rename to boa_types/src/tagged.rs