What it is
Codex is OpenAI's software engineering agent. It can work locally on your machine through the Codex CLI, the IDE extension and the ChatGPT desktop app, or in the cloud, where it runs tasks in a sandbox against your repository and returns changes for review. Local and cloud work draw from the same allowance.
Codex is not sold separately. It comes with ChatGPT plans: Free and Go get GPT-6 Luna in the desktop app as access rolls out, while Plus and above add the CLI, IDE extension, web, iOS and cloud features such as automatic code review and Slack, with GPT-6.1 Sol, GPT-6 Astra and GPT-6 Luna. You can also sign in with an API key and pay per token, though that skips the cloud features.
OpenAI retired GPT-5.5 from Codex for ChatGPT sign-ins on October 14, 2026, and made GPT-6.1 Sol the default.
Our review
Codex's selling point is that it costs nothing extra. A $20 ChatGPT Plus subscription brings an agent in the terminal, IDE, desktop app, web and iOS, plus cloud tasks that run against a repository and come back as a diff. OpenAI's pricing page estimates 15 to 160 local messages per 5 hours with GPT-6.1 Sol, or 350 to 3,000 with GPT-6 Luna, so routing simple edits to Luna stretches a Plus allowance a long way.
The local defaults are sensible. According to OpenAI's security docs, the CLI and IDE extension run in an OS-enforced sandbox that limits writes to the workspace, keeps network access off and asks before commands such as git push or npm install. The --yolo flag removes both guards and is documented for externally hardened environments only.
Training defaults split along plan lines. On Free, Plus and Pro, Codex tasks are covered by ChatGPT's "Improve the model for everyone" setting, which is on unless you turn it off, and a separate Codex setting decides whether whole environments can be used. Business seats, at $20 a user a month on annual billing with a two-user minimum, are excluded from training by default and add SAML SSO; SCIM, audit logs through the Compliance API and residency controls are Enterprise items.
The offer does not hold still. GPT-5.5 left Codex for ChatGPT sign-ins on October 14, a fortnight after GPT-6.1 Sol became the default, and forum users complained that Sol is not a drop-in replacement. The 5-hour figures are estimates, weekly limits may apply on top, and Ultrafast mode on the $500 Pro tier burns included usage 8x faster. Claude Code's hooks, skills and plugin ecosystem remain deeper; Codex wins on what a ChatGPT subscriber pays for the first month.
Where it earns its place
A freelance developer already on ChatGPT Plus
Fix bugs and write tests from the terminal without another bill
Run the CLI with GPT-6 Luna for routine edits and switch to GPT-6.1 Sol for harder ones; Plus at $20 covers both. Turn off "Improve the model for everyone" and the Codex environments setting before pointing it at client code.
A 15-developer team on GitHub
Get automatic code review on every pull request
Business at $20 a seat on annual billing is $300 a month, includes cloud code review and larger cloud machines, and keeps code out of training by default. Heavy review days can hit the per-seat limits, so budget for extra credits.
A platform team running Codex in CI
Script fixes and migrations without a ChatGPT seat per bot
Sign in with an API key and pay standard per-token rates; there is no 5-hour window, but there are no cloud features either. Pin the model with --model so a default change does not alter results.
Before you commit
- Setup
- Install the CLI or IDE extension and sign in with a ChatGPT account or an API key; the desktop app needs only a ChatGPT login.
- Integrations
- Terminal, VS Code-compatible IDEs, ChatGPT desktop and iOS, GitHub code review, Slack, MCP servers and Amazon Bedrock.
- Data and privacy
- Free, Plus and Pro tasks can train models unless you opt out in ChatGPT data controls; Business, Enterprise and API data is excluded by default. SCIM, EKM and residency controls are Enterprise-only.
- Cost at scale
- A 40-developer team on Business pays $800 a month on annual billing or $1,000 monthly, plus purchased credits when people exceed per-seat limits.
- Limits
- Plus is metered per 5 hours with possible weekly caps; Pro has no 5-hour limit for now; Fast mode uses 2.5x and Ultrafast 8x included usage.
What's good
- Included with ChatGPT Plus and Business at no extra cost
- Local sandbox blocks network access and asks before risky commands
- One allowance covers CLI, IDE, desktop, web and cloud tasks
- GPT-6 Luna gives 350 to 3,000 messages per 5 hours on Plus
- API-key sign-in for pay-per-token use
What's not
- Personal plans train on Codex tasks unless you opt out
- Models and limits change with little notice
- Usage figures are estimates and weekly caps are unpublished
- API-key mode has no cloud review or Slack features
Best for
Developers and teams already paying for ChatGPT who want a terminal and cloud coding agent without a separate subscription.
Alternatives
Head to head
OpenAI Codex: common questions
- Is OpenAI Codex worth it?
- Codex is the coding agent most developers already own through ChatGPT, and its main weakness is that OpenAI keeps changing what that ownership buys. We rate it 4.5 out of 5.
- How much does OpenAI Codex cost?
- Free and Go ($8/month): GPT-6 Luna in the desktop app, rolling out. Plus $20/month with usage measured per 5 hours. Pro $100, $200 or $500/month with no five-hour limit for now (Ultrafast mode only at $500). Business $20/user/month yearly (2-user minimum) or $25 monthly. Enterprise and Edu via sales. Extra credits can be bought.
- What are the downsides of OpenAI Codex?
- Personal plans train on Codex tasks unless you opt out; models and limits change with little notice; usage figures are estimates and weekly caps are unpublished; aPI-key mode has no cloud review or Slack features.
- Who is OpenAI Codex best for?
- Developers and teams already paying for ChatGPT who want a terminal and cloud coding agent without a separate subscription.
- How much does OpenAI Codex cost for a team or in production?
- A 40-developer team on Business pays $800 a month on annual billing or $1,000 monthly, plus purchased credits when people exceed per-seat limits.
- Is OpenAI Codex safe for company data?
- Free, Plus and Pro tasks can train models unless you opt out in ChatGPT data controls; Business, Enterprise and API data is excluded by default. SCIM, EKM and residency controls are Enterprise-only.
- What are the best OpenAI Codex alternatives?
- The closest alternatives we have reviewed are Claude Code, Cursor, GitHub Copilot and Google Antigravity (with Gemini CLI and Jules).
Answers checked Oct 22, 2026.
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