diff --git a/.cargo/config.toml b/.cargo/config.toml
new file mode 100644
index 0000000..428ed22
--- /dev/null
+++ b/.cargo/config.toml
@@ -0,0 +1,2 @@
+[target.wasm32-wasip1]
+runner = ["./scripts/wasmtime-wrapper.sh"]
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index a92d664..7240575 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -28,3 +28,22 @@ jobs:
         run: cp Cargo.lock.msrv Cargo.lock
       - name: Test
         run: cargo check --all-features
+
+  test-wasi:
+    name: Test on WASI
+    runs-on: ubuntu-latest
+  
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: stable
+          targets: wasm32-wasip1
+      - uses: Swatinem/rust-cache@v2
+      - name: Install WasmTime
+        run: |
+          curl -LO https://github.com/bytecodealliance/wasmtime/releases/download/v13.0.0/wasmtime-v13.0.0-x86_64-linux.tar.xz
+          tar xvf wasmtime-v13.0.0-x86_64-linux.tar.xz
+          echo `pwd`/wasmtime-v13.0.0-x86_64-linux >> $GITHUB_PATH
+      - name: Test
+        run: make wasi-test
diff --git a/Makefile b/Makefile
index af6e831..bb51dbf 100644
--- a/Makefile
+++ b/Makefile
@@ -12,6 +12,10 @@ test:
 	@cargo test --no-default-features
 	@cargo test --no-default-features --features bytes
 
+.PHONY: wasi-test
+wasi-test:
+	@cargo test --all-features --target=wasm32-wasip1 -- --nocapture
+
 format:
 	@rustup component add rustfmt 2> /dev/null
 	@cargo fmt --all
diff --git a/scripts/wasmtime-wrapper.sh b/scripts/wasmtime-wrapper.sh
new file mode 100755
index 0000000..d6ece59
--- /dev/null
+++ b/scripts/wasmtime-wrapper.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+cd $SCRIPT_DIR/..
+wasmtime run --max-wasm-stack=4194304 --env INSTA_WORKSPACE_ROOT=/ --mapdir "/::$(pwd)" -- "$@"
diff --git a/src/algorithms/lcs.rs b/src/algorithms/lcs.rs
index 5f081db..1c6a43b 100644
--- a/src/algorithms/lcs.rs
+++ b/src/algorithms/lcs.rs
@@ -7,7 +7,7 @@ use std::ops::{Index, Range};
 
 use crate::algorithms::utils::{common_prefix_len, common_suffix_len, is_empty_range};
 use crate::algorithms::DiffHook;
-use crate::Instant;
+use crate::deadline_support::{deadline_exceeded, Instant};
 
 /// LCS diff algorithm.
 ///
@@ -166,10 +166,8 @@ where
 
     for i in (0..new_len).rev() {
         // are we running for too long?  give up on the table
-        if let Some(deadline) = deadline {
-            if Instant::now() > deadline {
-                return None;
-            }
+        if deadline_exceeded(deadline) {
+            return None;
         }
 
         for j in (0..old_len).rev() {
diff --git a/src/algorithms/mod.rs b/src/algorithms/mod.rs
index 0953cd7..008ade5 100644
--- a/src/algorithms/mod.rs
+++ b/src/algorithms/mod.rs
@@ -42,7 +42,7 @@ pub(crate) mod utils;
 use std::hash::Hash;
 use std::ops::{Index, Range};
 
-use crate::Instant;
+use crate::deadline_support::Instant;
 pub use capture::Capture;
 pub use compact::Compact;
 pub use hook::{DiffHook, NoFinishHook};
diff --git a/src/algorithms/myers.rs b/src/algorithms/myers.rs
index 20ddf6c..c6c1bf7 100644
--- a/src/algorithms/myers.rs
+++ b/src/algorithms/myers.rs
@@ -23,7 +23,7 @@ use std::ops::{Index, IndexMut, Range};
 
 use crate::algorithms::utils::{common_prefix_len, common_suffix_len, is_empty_range};
 use crate::algorithms::DiffHook;
-use crate::Instant;
+use crate::deadline_support::{deadline_exceeded, Instant};
 
 /// Myers' diff algorithm.
 ///
@@ -175,10 +175,8 @@ where
 
     for d in 0..d_max as isize {
         // are we running for too long?
-        if let Some(deadline) = deadline {
-            if Instant::now() > deadline {
-                break;
-            }
+        if deadline_exceeded(deadline) {
+            break;
         }
 
         // Forward path
diff --git a/src/algorithms/patience.rs b/src/algorithms/patience.rs
index 1cce122..c207c03 100644
--- a/src/algorithms/patience.rs
+++ b/src/algorithms/patience.rs
@@ -12,7 +12,7 @@ use std::hash::Hash;
 use std::ops::{Index, Range};
 
 use crate::algorithms::{myers, DiffHook, NoFinishHook, Replace};
-use crate::Instant;
+use crate::deadline_support::Instant;
 
 use super::utils::{unique, UniqueItem};
 
diff --git a/src/common.rs b/src/common.rs
index d7c8e14..8ce9a92 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -2,7 +2,7 @@ use std::hash::Hash;
 use std::ops::{Index, Range};
 
 use crate::algorithms::{diff_deadline, Capture, Compact, Replace};
-use crate::Instant;
+use crate::deadline_support::Instant;
 use crate::{Algorithm, DiffOp};
 
 /// Creates a diff between old and new with the given algorithm capturing the ops.
diff --git a/src/deadline_support.rs b/src/deadline_support.rs
new file mode 100644
index 0000000..1066d41
--- /dev/null
+++ b/src/deadline_support.rs
@@ -0,0 +1,37 @@
+use std::time::Duration;
+
+#[cfg(not(feature = "wasm32_web_time"))]
+pub use std::time::Instant;
+
+/// WASM (browser) specific instant type.
+///
+/// This type is only available when the `wasm32_web_time` feature is enabled.  In that
+/// case this is an alias for [`web_time::Instant`].
+#[cfg(feature = "wasm32_web_time")]
+pub use web_time::Instant;
+
+/// Checks if a deadline was exeeded.
+pub fn deadline_exceeded(deadline: Option<Instant>) -> bool {
+    #[allow(unreachable_code)]
+    match deadline {
+        Some(deadline) => {
+            #[cfg(all(target_arch = "wasm32", not(feature = "wasm32_web_time")))]
+            {
+                return false;
+            }
+            Instant::now() > deadline
+        }
+        None => false,
+    }
+}
+
+/// Converst a duration into a deadline.  This can be a noop on wasm
+#[allow(unused)]
+pub fn duration_to_deadline(add: Duration) -> Option<Instant> {
+    #[allow(unreachable_code)]
+    #[cfg(all(target_arch = "wasm32", not(feature = "wasm32_web_time")))]
+    {
+        return None;
+    }
+    Instant::now().checked_add(add)
+}
diff --git a/src/lib.rs b/src/lib.rs
index b558863..3b09bc2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -121,6 +121,11 @@
 //! The [`TextDiff`] type also lets you configure a deadline and/or timeout
 //! when performing a text diff.
 //!
+//! Note that on wasm targets calling [`Instant::now`] will result in a panic
+//! unless you enable the `wasm32_web_time` feataure.  By default similar will
+//! silently disable the deadline checks internally unless that feature is
+//! enabled.
+//!
 //! # Feature Flags
 //!
 //! The crate by default does not have any dependencies however for some use
@@ -156,6 +161,7 @@ pub mod udiff;
 pub mod utils;
 
 mod common;
+mod deadline_support;
 #[cfg(feature = "text")]
 mod text;
 mod types;
@@ -165,13 +171,6 @@ pub use self::common::*;
 pub use self::text::*;
 pub use self::types::*;
 
-/// Internal alias for portability
-#[cfg(not(feature = "wasm32_web_time"))]
-pub(crate) use std::time::Instant;
-
-/// WASM (browser) specific instant type.
-///
-/// This type is only available when the `wasm32_web_time` feature is enabled.  In that
-/// case this is an alias for [`web_time::Instant`].
+// re-export the type for web-time feature
 #[cfg(feature = "wasm32_web_time")]
-pub use web_time::Instant;
+pub use deadline_support::Instant;
diff --git a/src/text/inline.rs b/src/text/inline.rs
index 3052784..bd2fd5d 100644
--- a/src/text/inline.rs
+++ b/src/text/inline.rs
@@ -1,9 +1,9 @@
 use std::borrow::Cow;
 use std::fmt;
 
+use crate::deadline_support::Instant;
 use crate::text::{DiffableStr, TextDiff};
 use crate::types::{Algorithm, Change, ChangeTag, DiffOp, DiffTag};
-use crate::Instant;
 use crate::{capture_diff_deadline, get_diff_ratio};
 
 use std::ops::Index;
diff --git a/src/text/mod.rs b/src/text/mod.rs
index ca6ca97..5acf114 100644
--- a/src/text/mod.rs
+++ b/src/text/mod.rs
@@ -15,9 +15,9 @@ pub use self::inline::InlineChange;
 
 use self::utils::{upper_seq_ratio, QuickSeqRatio};
 use crate::algorithms::IdentifyDistinct;
+use crate::deadline_support::{duration_to_deadline, Instant};
 use crate::iter::{AllChangesIter, ChangesIter};
 use crate::udiff::UnifiedDiff;
-use crate::Instant;
 use crate::{capture_diff_deadline, get_diff_ratio, group_diff_ops, Algorithm, DiffOp};
 
 #[derive(Debug, Clone, Copy)]
@@ -27,10 +27,10 @@ enum Deadline {
 }
 
 impl Deadline {
-    fn into_instant(self) -> Instant {
+    fn into_instant(self) -> Option<Instant> {
         match self {
-            Deadline::Absolute(instant) => instant,
-            Deadline::Relative(duration) => Instant::now() + duration,
+            Deadline::Absolute(instant) => Some(instant),
+            Deadline::Relative(duration) => duration_to_deadline(duration),
         }
     }
 }
@@ -319,7 +319,7 @@ impl TextDiffConfig {
         new: Cow<'bufs, [&'new T]>,
         newline_terminated: bool,
     ) -> TextDiff<'old, 'new, 'bufs, T> {
-        let deadline = self.deadline.map(|x| x.into_instant());
+        let deadline = self.deadline.and_then(|x| x.into_instant());
         let ops = if old.len() > 100 || new.len() > 100 {
             let ih = IdentifyDistinct::<u32>::new(&old[..], 0..old.len(), &new[..], 0..new.len());
             capture_diff_deadline(
@@ -548,7 +548,9 @@ impl<'old, 'new, 'bufs, T: DiffableStr + ?Sized + 'old + 'new> TextDiff<'old, 'n
     where
         'slf: 'old + 'new,
     {
-        inline::iter_inline_changes(self, op, Some(Instant::now() + Duration::from_millis(500)))
+        use crate::deadline_support::duration_to_deadline;
+
+        inline::iter_inline_changes(self, op, duration_to_deadline(Duration::from_millis(500)))
     }
 
     /// Iterates over the changes the op expands to with inline emphasis with a deadline.