Source: https://seerepo.com/compare/harvard-edge/cs249r_book/vs/mozilla-mobile/firefox-ios
Markdown source: https://seerepo.com/compare/harvard-edge/cs249r_book/vs/mozilla-mobile/firefox-ios.md
Description: cs249r_book and firefox-ios share 6 technologies: Rich, jinja2, markdown-it-py, markupsafe, mdurl, and dompurify. cs249r_book is written in Python and firefox-ios in Swift.

# cs249r_book vs firefox-ios

cs249r_book and firefox-ios share 6 technologies: Rich, jinja2, markdown-it-py, markupsafe, mdurl, and dompurify. cs249r_book is written in Python and firefox-ios in Swift.

- [harvard-edge/cs249r_book](https://seerepo.com/r/harvard-edge/cs249r_book): Machine Learning Systems: Foundations, Scaling, Agentic AI, and Physical AI (Vols I–IV) • Harvard CS249r | https://mlsysbook.ai
- [mozilla-mobile/firefox-ios](https://seerepo.com/r/mozilla-mobile/firefox-ios): Firefox for iOS

## What they share and what sets them apart

- In common: Rich, jinja2, markdown-it-py, markupsafe, mdurl, dompurify
- Only in cs249r_book: async-lru, pyzmq, requests-cache, pyarrow, anyio, jupyter-core, jupyterlab-server, tornado, Vite, React, idb, Next.js, cycler, fonttools, jupyterlab-pygments, soupsieve, tinycss2, contourpy, ipywidgets, jupyter-server-terminals, jupyterlab-widgets, matplotlib-inline, prompt-toolkit, seaborn, widgetsnbextension, matplotlib, Plotly, argon2-cffi, argon2-cffi-bindings, groq, Ollama, OpenAI, torch, transformers, torchvision, scikit-learn, sentence-transformers, librosa, nltk, torch-geometric, bleach, defusedxml, ghostscript, mistune, nbconvert, pandocfilters, pylatexenc, pypandoc, python-frontmatter, tablib, webencodings, xlrd, xlwt, xmltodict, beautifulsoup4, pillow, lxml, jupytext, nbformat, annotated-types, cattrs, fastjsonschema, fqdn, jsonschema-specifications, referencing, rfc3339-validator, rfc3986-validator, Pydantic, jsonschema, pydantic-core, prometheus-client, python-json-logger, psutil, Tailwind CSS, Mermaid, Chart.js, D3, compromise, katex, markdown-it, markdown-it-container, jspdf, jspdf-autotable, Framer, react-medium-image-zoom, Lucide
- Only in firefox-ios: Sentry, SnapKit, @mozilla/readability, SwiftDraw, voluptuous, SwiftyBeaver

## Side by side

| | cs249r_book | firefox-ios |
|---|---|---|
| Size | 821,581 lines written, 1,977 code files | 592,956 lines written, 2,242 code files |
| Who writes it | 2.7% of its commits signed by AI. With Codex, Claude Code, Gemini CLI, and Cursor | 0.2% of its commits signed by AI. With Claude Code, GitHub Copilot, and Cursor |
| Activity | Last push November 8, 2026, 22,351 commits, 30,011 stars | Last push November 10, 2026, 20,850 commits, 13,068 stars |
| Tests | 629 test files. 16.6% of its code files have a test that imports them | 1,280 test files. 54.3% of its code files have a test that imports them |

- Size: Lines written by people and agents, without generated ones; code files, without tests.
- Who writes it: A commit counts as AI's when it carries its signature: a Co-Authored-By line, its author name or the merge of its branch.
- Activity: From GitHub and its history, on the day SeeRepo read it.
- Tests: The files that test the code, and the share of code files a test imports.

## Frequently asked questions

### Which is bigger, cs249r_book or firefox-ios?

cs249r_book, with 821,581 lines written; firefox-ios has 592,956.

The proof: [harvard-edge/cs249r_book's code at commit de87c01](https://github.com/harvard-edge/cs249r_book/tree/de87c0103806d7bfb1c677dbb77a2b92fa00c298)

### Which has more GitHub stars, cs249r_book or firefox-ios?

cs249r_book, with 30,011 stars; firefox-ios has 13,068.

The proof: [harvard-edge/cs249r_book on GitHub](https://github.com/harvard-edge/cs249r_book)

### Which has more tests, cs249r_book or firefox-ios?

firefox-ios, with 1,280 test files; cs249r_book has 629.

The proof: [mozilla-mobile/firefox-ios's code at commit 81b5f3a](https://github.com/mozilla-mobile/firefox-ios/tree/81b5f3ab6442df317734d1d363532d262d4f78cf)

### Which was updated more recently, cs249r_book or firefox-ios?

firefox-ios: its last push was on November 10, 2026, and cs249r_book's on November 8, 2026.

The proof: [mozilla-mobile/firefox-ios's commits on GitHub](https://github.com/mozilla-mobile/firefox-ios/commits)

### Which has more commits signed by AI, cs249r_book or firefox-ios?

cs249r_book: an AI signed 2.7% of its commits, with Codex, Claude Code, Gemini CLI, and Cursor; in firefox-ios, 0.2%.

The proof: [the commits each tool signed in harvard-edge/cs249r_book](https://seerepo.com/r/harvard-edge/cs249r_book/ai)

## Sources

- harvard-edge/cs249r_book: Read on November 8, 2026, at commit de87c01 (https://github.com/harvard-edge/cs249r_book/tree/de87c0103806d7bfb1c677dbb77a2b92fa00c298)
- mozilla-mobile/firefox-ios: Read on November 10, 2026, at commit 81b5f3a (https://github.com/mozilla-mobile/firefox-ios/tree/81b5f3ab6442df317734d1d363532d262d4f78cf)

## What is your repo built with?

Any public repo, with no account: https://seerepo.com/r/owner/repo/built, with the owner and name it has on GitHub.