Simon Willison's Weblog: servo

Exploring the new `servo` crate

2026-04-13T15:04:00+00:00

Research: Exploring the new `servo` crate

In Servo is now available on crates.io the Servo team announced the initial release of the servo crate, which packages their browser engine as an embeddable library.

I set Claude Code for web the task of figuring out what it can do, building a CLI tool for taking screenshots using it and working out if it could be compiled to WebAssembly.

The servo-shot Rust tool it built works pretty well:

git clone https://github.com/simonw/research
cd research/servo-crate-exploration/servo-shot
cargo build
./target/debug/servo-shot https://news.ycombinator.com/

Here's the result:

Compiling Servo itself to WebAssembly is not feasible due to its heavy use of threads and dependencies like SpiderMonkey, but Claude did build me this playground page for trying out a WebAssembly build of the html5ever and markup5ever_rcdom crates, providing a tool for turning fragments of HTML into a parse tree.

Tags: browsers, research, rust, webassembly, servo, claude-code

Quoting Contributing to Servo

2025-05-12T22:14:30+00:00

Contributions must not include content generated by large language models or other probabilistic tools, including but not limited to Copilot or ChatGPT. This policy covers code, documentation, pull requests, issues, comments, and any other contributions to the Servo project. [...]

Our rationale is as follows:

Maintainer burden: Reviewers depend on contributors to write and test their code before submitting it. We have found that these tools make it easy to generate large amounts of plausible-looking code that the contributor does not understand, is often untested, and does not function properly. This is a drain on the (already limited) time and energy of our reviewers.

Correctness and security: Even when code generated by AI tools does seem to function, there is no guarantee that it is correct, and no indication of what security implications it may have. A web browser engine is built to run in hostile execution environments, so all code must take into account potential security issues. Contributors play a large role in considering these issues when creating contributions, something that we cannot trust an AI tool to do.

Copyright issues: [...] Ethical issues:: [...] These are harms that we do not want to perpetuate, even if only indirectly.

— Contributing to Servo, section on AI contributions

Tags: browsers, ai, generative-ai, servo, llms, ai-assisted-programming, ai-ethics

This month in Servo: parallel tables and more

2024-07-31T15:03:28+00:00

This month in Servo: parallel tables and more

New in Servo:

Parallel table layout is now enabled (@mrobinson, #32477), spreading the work for laying out rows and their columns over all available CPU cores. This change is a great example of the strengths of Rayon and the opportunistic parallelism in Servo's layout engine.

The commit landing the change is quite short, and much of the work is done by refactoring the code to use .par_iter().enumerate().map(...) - par_iter() is the Rayon method that allows parallel iteration over a collection using multiple threads, hence multiple CPU cores.

Via Phoronix

Tags: concurrency, html, rust, servo

Servo to Advance in 2023

2023-01-16T17:08:00+00:00

Servo to Advance in 2023

This is excellent news: Servo, the browser-in-Rust project started by Mozilla in 2012 that produced the Rust programming language, is getting re-activated with four new full-time developers provided by Igalia.

Igalia are a fascinating organization - I hadn't realized quite how influential they've been until I read their Wikipedia page just now

They've been around since 2001, and "in 2019 they were the #2 committers to both the WebKit and Chromium codebases and in the top 10 contributors to Gecko/Servo" - including implementing and maintaining CSS Grid Layout!

Via Hacker News

Tags: browsers, rust, servo, igalia

Boiling the Ocean, Incrementally - How Stylo Brought Rust and Servo to Firefox

2017-11-28T20:34:43+00:00

Boiling the Ocean, Incrementally - How Stylo Brought Rust and Servo to Firefox

Firefox Quantum is the product of an impressive, highly risky chain of software engineering—Rust, Servo, then Stylo.

Tags: firefox, rust, servo

Entering the Quantum Era—How Firefox got fast again and where it’s going to get faster

2017-11-13T16:34:44+00:00

Entering the Quantum Era—How Firefox got fast again and where it’s going to get faster

I’ve been trying out the beta of Firefox 57 and it’s fantastic. All of that work on Servo and Rust is definitely paying off!

Tags: firefox, rust, servo