diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index ddf68ef01..cdbf06f9b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -116,7 +116,7 @@ jobs:
         uses: actions/checkout@v3
       - run: cargo check --all-targets --no-default-features
       # we don't want to test `proj-network` because it only enables the `proj` feature
-      - run: cargo test --features "use-proj use-serde"
+      - run: cargo test --features "use-proj use-serde i_overlay earcutr multithreading"
 
   geo_traits:
     name: geo-traits
diff --git a/geo/Cargo.toml b/geo/Cargo.toml
index c8cc5f188..9c29776ce 100644
--- a/geo/Cargo.toml
+++ b/geo/Cargo.toml
@@ -13,10 +13,11 @@ rust-version = "1.75"
 categories = ["science::geo"]
 
 [features]
-default = ["earcutr", "spade"]
+default = ["earcutr", "spade", "i_overlay", "multithreading"]
 use-proj = ["proj"]
 proj-network = ["use-proj", "proj/network"]
 use-serde = ["serde", "geo-types/serde"]
+multithreading = ["i_overlay/allow_multithreading"]
 
 [dependencies]
 earcutr = { version = "0.4.2", optional = true }
@@ -30,7 +31,7 @@ proj = { version = "0.27.0", optional = true }
 robust = "1.1.0"
 rstar = "0.12.0"
 serde = { version = "1.0", optional = true, features = ["derive"] }
-i_overlay = "1.7.2"
+i_overlay = { version = "1.7.2", optional = true }
 
 [dev-dependencies]
 approx = ">= 0.4.0, < 0.6.0"
diff --git a/geo/src/algorithm/bool_ops/mod.rs b/geo/src/algorithm/bool_ops/mod.rs
index 16287b049..aa5abdf02 100644
--- a/geo/src/algorithm/bool_ops/mod.rs
+++ b/geo/src/algorithm/bool_ops/mod.rs
@@ -8,6 +8,8 @@ use crate::geometry::{LineString, MultiLineString, MultiPolygon, Polygon};
 
 /// Boolean Operations on geometry.
 ///
+/// Requires the `"i_overlay"` feature, which is enabled by default.
+///
 /// Boolean operations are set operations on geometries considered as a subset
 /// of the 2-D plane. The operations supported are: intersection, union, xor or
 /// symmetric difference, and set-difference on pairs of 2-D geometries and
diff --git a/geo/src/algorithm/mod.rs b/geo/src/algorithm/mod.rs
index 344084dc3..b47f1c56d 100644
--- a/geo/src/algorithm/mod.rs
+++ b/geo/src/algorithm/mod.rs
@@ -6,8 +6,12 @@ pub use kernels::{Kernel, Orientation};
 pub mod area;
 pub use area::Area;
 
-/// Boolean Ops such as union, xor, difference;
+/// Boolean Ops such as union, xor, difference.
+///
+/// Requires the `"i_overlay"` feature, which is enabled by default.
+#[cfg(feature = "i_overlay")]
 pub mod bool_ops;
+#[cfg(feature = "i_overlay")]
 pub use bool_ops::{BooleanOps, OpType};
 
 /// Calculate the bounding rectangle of a `Geometry`.
@@ -254,6 +258,8 @@ pub mod translate;
 pub use translate::Translate;
 
 /// Triangulate polygons using an [ear-cutting algorithm](https://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf).
+///
+/// Requires the `"earcutr"` feature.
 #[cfg(feature = "earcutr")]
 pub mod triangulate_earcut;
 #[cfg(feature = "earcutr")]
diff --git a/geo/src/algorithm/triangulate_earcut.rs b/geo/src/algorithm/triangulate_earcut.rs
index d4d23df32..586f3cb3d 100644
--- a/geo/src/algorithm/triangulate_earcut.rs
+++ b/geo/src/algorithm/triangulate_earcut.rs
@@ -1,6 +1,8 @@
 use crate::{coord, CoordFloat, CoordsIter, Polygon, Triangle};
 
 /// Triangulate polygons using an [ear-cutting algorithm](https://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf).
+///
+/// Requires the `"earcutr"` feature, which is enabled by default.
 pub trait TriangulateEarcut<T: CoordFloat> {
     /// # Examples
     ///
diff --git a/geo/src/lib.rs b/geo/src/lib.rs
index 11cf8bc4a..ff5bdf94a 100644
--- a/geo/src/lib.rs
+++ b/geo/src/lib.rs
@@ -67,7 +67,7 @@
 //!
 //! ## Boolean Operations
 //!
-//! - **[`BooleanOps`]**: combine or split (Multi)Polygons using intersecton, union, xor, or difference operations
+//! - **[`BooleanOps`]**: combine or split (Multi)Polygons using intersecton, union, xor, or difference operations. Requires the `"i_overlay"` feature, which is enabled by default.
 //!
 //! ## Outlier Detection
 //!
@@ -112,7 +112,7 @@
 //!
 //! ## Triangulation
 //!
-//! - **[`TriangulateEarcut`](triangulate_earcut)**: Triangulate polygons using the earcut algorithm (requires the `earcutr` feature).
+//! - **[`TriangulateEarcut`](triangulate_earcut)**: Triangulate polygons using the earcut algorithm. Requires the `"earcutr"` feature, which is enabled by default.
 //!
 //! ## Winding
 //!
@@ -177,9 +177,25 @@
 //!
 //! The following optional [Cargo features] are available:
 //!
-//! - `proj-network`: Enables [network grid] support for the [`proj` crate]. After enabling this feature, [further configuration][proj crate file download] is required to use the network grid
-//! - `use-proj`: Enables coordinate conversion and transformation of `Point` geometries using the [`proj` crate]
-//! - `use-serde`: Allows geometry types to be serialized and deserialized with [Serde]
+//! - `i_overlay`:
+//!     - Enables the `i_overlay` crate, which provides boolean operations on geometries.
+//!     - ☑ Enabled by default.
+//! - `earcutr`:
+//!     - Enables the `earcutr` crate, which provides triangulation of polygons using the earcut algorithm.
+//!     - ☑ Enabled by default.
+//! - `proj-network`:
+//!     - Enables [network grid] support for the [`proj` crate].
+//!     - After enabling this feature, [further configuration][proj crate file download] is required to use the network grid.
+//!     - ☐ Disabled by default.
+//! - `use-proj`:
+//!     - Enables coordinate conversion and transformation of `Point` geometries using the [`proj` crate]
+//!     - ☐ Disabled by default.
+//! - `use-serde`:
+//!     - Allows geometry types to be serialized and deserialized with [Serde].
+//!     - ☐ Disabled by default.
+//! - `multithreading`:
+//!     - Enables multithreading support for the `i_overlay` crate.
+//!     - ☑ Enabled by default.
 //!
 //! # Ecosystem
 //!