Compare GPT-5.3-Codex by OpenAI against Claude Sonnet 4 by Anthropic, context windows of 400K vs 200K, tested across 33 shared challenges. Updated April 2026.
GPT-5.3-Codex and Claude Sonnet 4 are both competitive models. GPT-5.3-Codex costs $1.75/M input tokens vs $3/M for Claude Sonnet 4. Context windows: 400K vs 200K tokens. Compare their real outputs side by side below.
GPT-5.3-Codex is made by openai while Claude Sonnet 4 is from anthropic. GPT-5.3-Codex has a 400K token context window compared to Claude Sonnet 4's 200K. On pricing, GPT-5.3-Codex costs $1.75/M input tokens vs $3/M for Claude Sonnet 4.
No community votes yet. On paper, GPT-5.3-Codex has the edge — bigger model tier, newer, bigger context window.
Claude Sonnet 4 uses 12.0x more transitions
Ask them anything yourself
Some models write identically. You are paying for the brand.
178 models fingerprinted across 32 writing dimensions. Free research.
185x
price gap between models that write identically
178
models
12
clone pairs
32
dimensions
279 AI models invented the same fake scientist.
We read every word. 250 models. 2.14 million words. This is what we found.

Compare GPT-5.3-Codex by OpenAI against Claude Sonnet 4 by Anthropic, context windows of 400K vs 200K, tested across 33 shared challenges. Updated April 2026.
GPT-5.3-Codex and Claude Sonnet 4 are both competitive models. GPT-5.3-Codex costs $1.75/M input tokens vs $3/M for Claude Sonnet 4. Context windows: 400K vs 200K tokens. Compare their real outputs side by side below.
GPT-5.3-Codex is made by openai while Claude Sonnet 4 is from anthropic. GPT-5.3-Codex has a 400K token context window compared to Claude Sonnet 4's 200K. On pricing, GPT-5.3-Codex costs $1.75/M input tokens vs $3/M for Claude Sonnet 4.
No community votes yet. On paper, GPT-5.3-Codex has the edge — bigger model tier, newer, bigger context window.
Claude Sonnet 4 uses 12.0x more transitions
Ask them anything yourself
Some models write identically. You are paying for the brand.
178 models fingerprinted across 32 writing dimensions. Free research.
185x
price gap between models that write identically
178
models
12
clone pairs
32
dimensions
279 AI models invented the same fake scientist.
We read every word. 250 models. 2.14 million words. This is what we found.

33 fights queued
Tests an AI's ability to solve a simple but potentially confusing logic puzzle
Tests an AI's randomness and creativity
Tests an AI's ability to generate vector graphics
Tests an AI's ability to create detailed SVG illustrations of gaming hardware
Tests an AI's humor and creative writing ability
Recreate an interactive, nostalgic Pokémon battle UI in a single HTML file.
Create a 3D building and driving game in a single self-contained HTML file using Three.js. Tests an AI's ability to combine 3D graphics, game logic, and UI interactions on the web.
Recreate an interactive, classic Mario level in a single HTML file.
Tests an AI's ability to replicate an existing UI with Tailwind CSS
Tests an AI's ability to create interactive web elements
Tests an AI's ability to create a detailed world map in SVG format
Generate a single-page, self-contained HTML webapp using Tailwind CSS for a randomly chosen category/industry/niche.
21+ more head-to-head results. Free. Not a trick.
Free account. No card required. By continuing, you agree to Rival's Terms and Privacy Policy
33 fights queued
Tests an AI's ability to solve a simple but potentially confusing logic puzzle
Tests an AI's randomness and creativity
Tests an AI's ability to generate vector graphics
Tests an AI's ability to create detailed SVG illustrations of gaming hardware
Tests an AI's humor and creative writing ability
Recreate an interactive, nostalgic Pokémon battle UI in a single HTML file.
Create a 3D building and driving game in a single self-contained HTML file using Three.js. Tests an AI's ability to combine 3D graphics, game logic, and UI interactions on the web.
Recreate an interactive, classic Mario level in a single HTML file.
Tests an AI's ability to replicate an existing UI with Tailwind CSS
Tests an AI's ability to create interactive web elements
Tests an AI's ability to create a detailed world map in SVG format
Generate a single-page, self-contained HTML webapp using Tailwind CSS for a randomly chosen category/industry/niche.
21+ more head-to-head results. Free. Not a trick.
Free account. No card required. By continuing, you agree to Rival's Terms and Privacy Policy