GPT-5.3 Codex vs Grok Code Fast 1

Compare OpenAI and xAI AI models

OpenAI

GPT-5.3 Codex

xAI

Grok Code Fast 1

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Cost Comparison (1000 input + 500 output tokens, 100 requests/day)

GPT-5.3 Codex

Per Request:$0.008750

Daily:$0.875

Monthly:$26.25

Yearly:$319.375

Grok Code Fast 1

Per Request:$0.000950

Daily:$0.095

Monthly:$2.85

Yearly:$34.675

Cost Differences

$0.007800

Per Request

$0.78

Daily

$23.40

Monthly

$284.70

Yearly

Grok Code Fast 1 costs less than GPT-5.3 Codex

Feature Comparison

Feature	GPT-5.3 Codex	Grok Code Fast 1
Provider	OpenAI	xAI
Input Price	$1.75/1M tokens	$0.20/1M tokens
Output Price	$14.00/1M tokens	$1.50/1M tokens
Context Window	256,000 tokens	256,000 tokens
Max Output	32,768 tokens	32,768 tokens
Category	coding	standard
Capabilities	textcode	textcodereasoning
Release Date	3/1/2026	2/1/2026

GPT-5.3 Codex vs Grok Code Fast 1: Which Should You Choose?

Choosing between GPT-5.3 Codex and Grok Code Fast 1 depends on your priorities: cost efficiency, context length, or raw capability. Grok Code Fast 1 is the more affordable option at $0.20/1M input tokens — 89% cheaper than GPT-5.3 Codex.

These models come from different providers — OpenAI and xAI — which means different API ecosystems, SDKs, rate limits, and terms of service. If you're already integrated with OpenAI, switching to xAIinvolves migration effort beyond just pricing. Factor in your existing infrastructure when deciding.

These models target different tiers: GPT-5.3 Codex is a coding model while Grok Code Fast 1 is standard. This means they're optimized for different workloads. Grok Code Fast 1 targets more demanding workloads, while GPT-5.3 Codex provides a cost-effective option for everyday tasks.

Output costs matter too. GPT-5.3 Codex charges $14.00/1M output tokens vs $1.50 for Grok Code Fast 1. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. Grok Code Fast 1 has the edge here at $1.50/1M output tokens.

Best Use Cases

Choose GPT-5.3 Codex when:

• You're already using OpenAI's API ecosystem

Choose Grok Code Fast 1 when:

• Budget is a primary concern
• You need more capabilities (reasoning)
• You're already using xAI's API ecosystem

Try Different Scenarios

Use the calculator below to see how costs change with different usage patterns

GPT-5.3 Codex (OpenAI)

Cost Calculator

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Model

Input Tokens

Output Tokens

Requests/Day

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Grok Code Fast 1 (xAI)

Cost Calculator

Provider

Model

Input Tokens

Output Tokens

Requests/Day

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Frequently Asked Questions

Which is cheaper, GPT-5.3 Codex or Grok Code Fast 1?▼

Grok Code Fast 1 is cheaper for input tokens at $0.20 per million tokens vs $1.75 for GPT-5.3 Codex — that's 89% savings on input costs.

What is the context window difference between GPT-5.3 Codex and Grok Code Fast 1?▼

GPT-5.3 Codex supports 256,000 tokens while Grok Code Fast 1 supports 256,000 tokens — a difference of 0 tokens in favor of GPT-5.3 Codex.

Which model is better for AI Chatbot?▼

Both models support text. For ai chatbot, Grok Code Fast 1 is the lower-cost option, while GPT-5.3 Codex offers a larger context window (256,000 vs 256,000 tokens). Choose Grok Code Fast 1 for budget sensitivity or GPT-5.3 Codex for longer context tasks.

Which model has better overall pricing for heavy usage?▼

At 100 requests/day with 1,000 input and 500 output tokens each, GPT-5.3 Codex costs about $26.25/month and Grok Code Fast 1 costs about $2.85/month. Overall, Grok Code Fast 1 has lower combined input + output rates ($0.20 in, $1.50 out) vs GPT-5.3 Codex.