GPT-5.3-Codex vs xAI: Grok 4 Fast (free)
Compare GPT-5.3-Codex by OpenAI against xAI: Grok 4 Fast (free) by xAI, context windows of 400K vs 2.0M, tested across 34 shared challenges. Updated April 2026.
Which is better, GPT-5.3-Codex or xAI: Grok 4 Fast (free)?
GPT-5.3-Codex and xAI: Grok 4 Fast (free) are both competitive models. GPT-5.3-Codex costs $1.75/M input tokens vs $0/M for xAI: Grok 4 Fast (free). Context windows: 400K vs 2000K tokens. Compare their real outputs side by side below.
Key Differences Between GPT-5.3-Codex and xAI: Grok 4 Fast (free)
GPT-5.3-Codex is made by openai while xAI: Grok 4 Fast (free) is from xai. GPT-5.3-Codex has a 400K token context window compared to xAI: Grok 4 Fast (free)'s 2000K. On pricing, GPT-5.3-Codex costs $1.75/M input tokens vs $0/M for xAI: Grok 4 Fast (free).
No community votes yet. On paper, GPT-5.3-Codex has the edge — bigger model tier, newer.
Style Comparison
GPT-5.3-Codex uses 15.8x more emoji
vs
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.
