Scripting overview

Run your own ExtendScript code inside the After Effects project before a job renders, for changes that functions and data assets can’t express

A script asset runs your own ExtendScript code inside the job’s After Effects project, right before the render starts. Use it when a change needs logic: loops, conditions, reading data files, or restructuring compositions.

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When to use a script

Reach for the simplest asset type that does the job. A script is the most flexible option, and also the one you have to maintain.

You want to	Use
Replace text, images, video, or audio in a layer	text, image, video, audio assets
Set one property or expression on a layer	A data asset
Style text, change layer timing, hide or remove layers	A function
Anything that needs logic, loops, files, or several steps	A script asset

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Before you start

• Scripting is turned on per team. If your team doesn’t have it, the API rejects any job with a script asset with 403 and the error code SCRIPTING_DISABLED. Contact [e-mail] to get it turned on.
• Scripts are ExtendScript. That’s the JavaScript dialect After Effects uses for scripting, based on ECMAScript 3. Use var and function. let, arrow functions, and template literals don’t work. Nexrender adds JSON.parse, JSON.stringify, and the array methods forEach, filter, and indexOf, which plain ExtendScript lacks.
• Scripts run in a sandbox by default. They can use the After Effects scripting API and files in the job’s folder, but not the rest of the machine. See Sandbox and limits.

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Your first script

Host the script anywhere the render node can download it, and reference it from the job:

Job payload

{
  "template": {
    "id": "YOUR_TEMPLATE_ID",
    "composition": "main"
  },
  "assets": [
    {
      "type": "script",
      "src": "https://example.com/scripts/set-title.jsx",
      "parameters": [
        { "key": "title", "value": "Hello from a script" }
      ]
    }
  ]
}

NX.get("title") reads a value from the job’s parameters, and nexrender.selectLayersByName finds the layer. Script assets and parameters and Helper functions cover both in detail.

src accepts:

• A public https:// URL. Google Drive and Dropbox share links work too: Nexrender converts them to direct downloads.
• An inline data: URL, for short scripts or quick tests: data:text/javascript;base64, followed by the script encoded in Base64.

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How a job runs your script

1. Download

   Nexrender downloads the template and every asset into a folder for the job.

2. Assemble

   It builds one After Effects script from your assets, in the order you list them in assets. Footage replacements, text and data assets, functions, and scripts all apply in that order, so a script sees every change made by the assets above it.

3. Run

   After Effects opens the project and runs the assembled script, then saves the project.

4. Render

   After Effects renders the job’s composition.

If a script throws an error, the job stops before rendering and fails. Start your own error messages with nexrender: to make them the job’s error word for word. See Stop the job with a clear error.

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See what your script did

Lines your script writes with nexrender.log go into the job’s render log, prefixed with NX:. Read the log with GET /jobs/{id}/logs, which returns it as plain text, or with the CLI:

nexrender job logs JOB_ID

Render log (excerpt)

NX: Title set to: Hello from a script

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Next steps

Script assets and parameters

Every field of a script asset, and how to pass values into your script

Helper functions

The nexrender object: find compositions and layers, replace footage, log

Examples

Tested scripts for common tasks

Sandbox and limits

What scripts can do on Nexrender Cloud, and the limits that apply