How to Make Videos with OpenAI Codex CLI

OpenAI Codex CLI is a coding agent that runs in your terminal. From your computer, you can direct Codex through text to work with files and developer tools. Codex can create and change code, run commands, inspect rendered output, and revise a video project. It does not generate finished video footage by itself. Connect it to tools such as Remotion, FFmpeg, segmentation models, speech tools, or a third-party video-generation skill.

Use Codex as the director and automation layer. Describe the video, ask it to build or update the project, render selected frames, inspect the result, and revise the code. A community example used this method to create a complete Remotion edit without a traditional timeline editor.

You need three pieces:

1. Codex CLI for planning, coding, and running commands.
2. A video engine such as Remotion or FFmpeg for composition and rendering.
3. Media tools or services for footage, narration, captions, music, and visual effects.

The sections below explain how to set up this workflow and when to use a ready-made video skill.

Choose a video-making approach

First, decide how much control you need over the production pipeline.

Build a Remotion project with Codex

Remotion is a React framework for creating videos with code. You describe scenes, text, timing, transitions, and effects in React components instead of moving clips on a timeline. Remotion then renders those components as video frames.

This approach works well when you need:

• Repeatable layouts
• Programmatic text animation
• Product demos or data-driven videos
• Precise timing
• Reusable scene components
• Editing with version control

Codex can create the project structure, write scene components, add assets, render the video, and fix errors. You still choose the media and check the final result.

Install a video-generation skill

A skill is an extension that gives Codex instructions and tools for a specialized task. Pexo describes a skill that accepts a plain-language video brief and sends shots to external video models. Its documented workflow accepts text, images, URLs, scripts, and audio, and exports MP4 files in vertical, horizontal, and square formats.

This route is faster when you want to describe the result instead of building the rendering pipeline. It uses a third-party service and API key, so check its access requirements before using private media or production files.

Chain several specialized skills

A larger pipeline can connect separate skills for importing assets, recording a browser, composing motion, creating speech and subtitles, dubbing, and post-processing. A Codex production pipeline describes four layers:

• Ingesting assets
• Motion composition
• Speech and subtitles
• Post-processing

This design suits automated product demos and web-to-video workflows. It requires more setup because each layer depends on the next one.

For a first project, use Remotion with a small number of scenes. Add segmentation, voice, captions, or external generation services only when the video requires them.

Install and start Codex CLI

The official Codex repository documents installation through npm, Homebrew, and standalone scripts. After installation, start the agent by running:

codex

Codex prompts you to sign in with ChatGPT. API-key authentication requires additional configuration, so use the documented authentication method that matches your environment.

Create a dedicated directory for the video project before starting the session:

mkdir product-demo-video
cd product-demo-video
codex

The project files depend on the video approach. For a Remotion project, ask Codex to create the project and explain each command before it installs packages, downloads models, accesses external services, or deletes files.

A useful opening request looks like this:

Create a small Remotion video project for a short product demo.

Use five scenes:
1. Opening title
2. Product problem
3. Product interface
4. Short feature sequence
5. Closing call to action

Use a 16:9 composition. Keep all timing in one configuration file,
use placeholder assets where media is missing, and add a render
script. Before changing files, show me the plan.

This prompt gives Codex a clear scope, scene count, aspect ratio, and implementation constraint. It also keeps the first session from becoming an open-ended request to “make a video.”

Build the video as scenes

A scene is a section of the video with its own visual purpose and timing. Ask Codex to build one scene at a time and render after each meaningful change. This makes errors easier to isolate than building the whole project in one pass.

For example, a product demo might use:

• An opening title with a short animated background
• A screen recording or mock interface
• Zooms or highlights that call out important controls
• Captions synchronized with narration
• A final call to action

Store scene content separately from timing and assets. Codex can then change the wording or replace a media file without rewriting the entire composition.

You can ask for a component structure such as:

Separate the video into reusable scene components.
Keep scene duration, colors, fonts, and asset paths in a shared
configuration file. Add a placeholder state when an asset is missing.

The project code holds the implementation. The important principle is to make each scene testable on its own.

For generated or recorded footage, describe the visual result in production terms. State the subject, camera movement, duration, aspect ratio, mood, and transition. If you use an external generation service, describe the mood and shot rather than assuming Codex will select the right model automatically.

Add footage, masks, narration, and captions

Codex coordinates the media tools, but each tool handles a different task.

A segmentation model separates the subject from its background. A tracked matte follows it across multiple frames. The OpenAI community example used SAM3 for a static segmentation mask and MatAnyone for a tracked foreground matte. The resulting layers were then composited in Remotion.

This technique supports effects such as:

• Placing a person over an animated background
• Revealing a product behind a subject
• Replacing the background
• Moving text around a tracked object

These models require more computing resources than a basic Remotion render. The community creator deployed SAM3 and MatAnyone on Modal because the available Mac hardware had limited CPU capacity. Treat remote execution as an infrastructure choice, not a requirement for every video.

For narration and subtitles, use word-level timestamps when animation needs to follow speech precisely. A timestamp transcript assigns a start and end time to each word. Codex can use that data to trigger emphasis, size changes, highlights, or caption transitions at the right moment.

Give Codex a direct instruction such as:

Use the word-level transcript timestamps to animate each emphasized
word when it begins. Keep captions inside the safe area and preserve
the original line breaks where possible.

A safe area is the part of the frame that remains visible after a platform crops or overlays the video. Keep important text away from the edges, especially for vertical social videos.

Make Codex review its own renders

One render is not enough. The output can reveal clipped text, missing assets, incorrect layer order, unreadable captions, or transitions that move too quickly.

The community workflow used a script to render selected frames from Remotion for inspection. Rendering selected frames is faster than rendering the entire video after every change. Ask Codex to render representative frames from the beginning, middle, and end of each scene, then inspect those images before producing the final export.

A practical review request is:

Render representative frames from every scene.
Inspect them for clipped text, missing assets, incorrect timing,
low contrast, and elements outside the safe area.
List the problems, fix the source code, and render the same frames again.

Use this review loop:

1. Codex changes the source code.
2. The renderer produces frames.
3. Codex inspects the output.
4. Codex fixes visible problems.
5. You approve the final render.

The creator behind the community example described this self-review loop as a recommendation from an OpenAI engineer. It is especially useful for code-generated video because a successful render only proves that the code executed. It does not prove that the edit communicates clearly.

Use parallel Codex sessions carefully

Separate Codex sessions can work on different parts of a storyboard. One session might prepare assets, another might build a title sequence, and a third might develop captions or a product-demo scene.

Parallel work becomes risky when multiple sessions edit the same files. Assign each session a directory or component, and combine the changes only after each part renders successfully. Keep shared configuration files small and stable so sessions do not overwrite timing or asset settings.

For a small project, one session is simpler. Use parallel sessions when the scenes have clear boundaries and each session has a defined output.

Use Pexo for a faster plain-language workflow

Pexo’s documented Codex workflow requires an external account and API key. Sign in to Pexo and copy the key. Install the skill in the Codex skills directory, configure the key, and start a new Codex session. Follow the current Pexo installation instructions, because skill paths and configuration details can change.

After installation, give Codex a brief that specifies:

• The subject
• The target platform
• The total length
• The number of shots
• The visual mood
• The music direction
• The aspect ratio
• Any reference images, script, URL, or audio

For example:

Create a short vertical product video for social media.
Use three shots: show the problem, demonstrate the interface,
and end with a clear call to action. Use a restrained technical mood,
fast pacing, readable captions, and the attached product screenshots.

Pexo recommends generating variants in the same conversation and describing the desired mood rather than naming a particular model. Its published example reports that a 15-second, three-shot video takes roughly 8 to 10 minutes from start to finish, though actual time depends on the external services, inputs, and revisions.

A managed skill reduces implementation work, while a custom Remotion project gives you direct control over scene logic, rendering, and asset handling.

Expect setup and rendering delays

Codex-driven video production reduces manual timeline work, but it does not make every video instant. The community creator reported an 8-to-9-hour process, with MatAnyone integration causing much of the difficulty. The same report says the workflow took longer than manual editing and did not run in real time.

Use this decision rule:

• Choose a custom pipeline when repeatability, code-based control, or specialized effects justify the setup time.
• Choose a video skill when you need a short draft from a plain-language brief.
• Choose a conventional editor for a one-off project that depends on fast visual judgment and manual timing.

Use the community code as a reference implementation. The creator says the code is open source but not polished and may not work unchanged in another environment.

A practical first project

Start with a small short video containing three scenes. Use placeholder images and simple text before adding segmentation or generated footage. Ask Codex to create the project, render sample frames, inspect them, and correct the layout.

Once the basic pipeline works, add one capability at a time:

1. Replace placeholders with product screenshots or recordings.
2. Add narration and word-level timestamps.
3. Synchronize captions and text animation.
4. Add foreground or background replacement with tracking.
5. Export more aspect ratios.
6. Automate the render and review commands.

This order keeps failures localized. If the first render combines remote models, audio generation, subtitles, and multiple parallel sessions, it will be hard to identify the source of a problem.