GPT-5.3 Codex vs o3

Compare OpenAI and OpenAI AI models

OpenAI

GPT-5.3 Codex

OpenAI

Try OpenAI →

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

o3

Per Request:$0.006000

Daily:$0.60

Monthly:$18.00

Yearly:$219.00

Cost Differences

$0.002750

Per Request

$0.275

Daily

$8.25

Monthly

$100.375

Yearly

o3 costs less than GPT-5.3 Codex

Feature Comparison

Feature	GPT-5.3 Codex	o3
Provider	OpenAI	OpenAI
Input Price	$1.75/1M tokens	$2.00/1M tokens
Output Price	$14.00/1M tokens	$8.00/1M tokens
Context Window	256,000 tokens	1,000,000 tokens
Max Output	32,768 tokens	131,072 tokens
Category	coding	reasoning
Capabilities	textcode	textreasoningvisioncode
Release Date	3/1/2026	4/16/2025

GPT-5.3 Codex vs o3: Which Should You Choose?

Choosing between GPT-5.3 Codex and o3 depends on your priorities: cost efficiency, context length, or raw capability. o3 is the more affordable option at $2.00/1M input tokens. Meanwhile, o3 offers a significantly larger context window at 1,000,000 tokens vs 256,000 for GPT-5.3 Codex.

These models target different tiers: GPT-5.3 Codex is a coding model while o3 is reasoning. This means they're optimized for different workloads. o3 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 $8.00 for o3. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. o3 has the edge here at $8.00/1M output tokens.

Multimodal capabilities: o3 supports vision (image inputs) while GPT-5.3 Codex is text-only. If your application needs image understanding, this narrows your choice.

Best Use Cases

Choose GPT-5.3 Codex when:

• Budget is a primary concern
• You're already using OpenAI's API ecosystem

Choose o3 when:

• You need a larger context window (1,000,000 tokens)
• You need more capabilities (reasoning, vision)
• You need longer outputs (up to 131,072 tokens)
• You're already using OpenAI'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

Provider

Model

Input Tokens

Output Tokens

Requests/Day

Select a provider and model to see costs

o3 (OpenAI)

Cost Calculator

Provider

Model

Input Tokens

Output Tokens

Requests/Day

Select a provider and model to see costs

Start using GPT-5.3 Codex today

Start using o3 today

Frequently Asked Questions

Which is cheaper, GPT-5.3 Codex or o3?▼

o3 is cheaper for input tokens at $2.00 per million tokens vs $1.75 for GPT-5.3 Codex.

What is the context window difference between GPT-5.3 Codex and o3?▼

GPT-5.3 Codex supports 256,000 tokens while o3 supports 1,000,000 tokens — a difference of 744,000 tokens in favor of o3.

Which model is better for AI Chatbot?▼

Both models support text. For ai chatbot, o3 is the lower-cost option, while o3 offers a larger context window (1,000,000 vs 256,000 tokens). Choose o3 for budget sensitivity or o3 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 o3 costs about $18.00/month. Overall, o3 has lower combined input + output rates ($2.00 in, $8.00 out) vs GPT-5.3 Codex.