Figma Weave Error 400: Troubleshooting Guide

A 400 Bad Request error from the Figma Weave API means the server received a request it cannot process. Unlike a 401 (Unauthorized) or 403 (Forbidden) error, a 400 error indicates that your credentials are valid, but the construction of your HTTP request is malformed, contains invalid parameters, or violates the schema requirements of the Weave endpoint.

Use this step-by-step guide to isolate and fix the source of the 400 Bad Request error in your integration.

Step 1: Check Your JSON Payload Syntax

The most common cause of a 400 error is malformed JSON in the request body. If your application dynamically generates JSON payloads, a trailing comma, missing quotation mark, or unescaped control character can break the structure.

1. Copy the raw payload your application sends to Figma Weave.
2. Paste it into an online JSON validator (such as JSONLint) to check for syntax compliance.
3. Verify that all property names and string values are enclosed in double quotes ("), not single quotes (').
4. Ensure numerical values, booleans, and nulls are not wrapped in quotes unless specified by the Figma Weave API schema.

Step 2: Validate Schema and Parameter Data Types

Figma Weave enforces strict type checking on its API endpoints. If an endpoint expects an integer and you pass a string representation of that number, the server will reject the request with a 400 error.

1. Open the official Figma Weave API reference docs for the specific endpoint you are calling.
2. Verify that every parameter in your request matches the required data type (e.g., string, boolean, array, or number).
3. Check for mandatory fields. Ensure you are not omitting required parameters like file_key, node_id, or weave_config settings.
4. Confirm that any enumerated fields (enums) use the exact capitalization and spelling required by the API.

Step 3: Format File Keys and Node IDs Correctly

If you pass an invalid Figma file key or malformed node ID in your request parameters, the Weave API will respond with a 400 Bad Request because it cannot locate the target design resources.

1. Locate your Figma file key. This is the alphanumeric string found in your Figma file URL: figma.com/file/[FILE_KEY]/[FILE_NAME].
2. Ensure you are passing only the raw, alphanumeric file key. Do not include slash characters or URL fragments.
3. Validate your Node IDs. Figma node IDs often contain colons (e.g., 12:345). In some programming languages or HTTP clients, colons in query parameters must be URL-encoded as %3A. Check if your SDK or HTTP library is double-encoding or failing to encode these characters.

Step 4: Verify Content-Type and Custom Headers

Figma Weave requires specific headers to process incoming API requests. If these are missing or configured incorrectly, the server will reject the payload.

1. Check your Content-Type header. Ensure it is set exactly to application/json.
2. If you are uploading or processing large design tokens, asset bundles, or raw SVG data, make sure your transmission method matches the expected encoding schema of the endpoint (e.g., Base64 vs. multipart form data).
3. Double-check any custom Figma versioning headers. If you pass an invalid or deprecated API version header, the gateway may return a 400 error.

Step 5: Test the Request via cURL or Postman

To rule out issues within your SDK, application framework, or state management library, isolate the network request using a clean terminal environment.

1. Construct a minimal bash curl request containing only the required headers, authentication tokens, and a basic JSON payload.
2. Execute the request directly from your terminal.
3. If the command succeeds with a 200 OK, the issue lies within your application code, serialization logic, or HTTP client configurations.
4. If the terminal request still fails with a 400 error, inspect the raw response body returned by the server. Figma Weave often provides a descriptive nested error object (such as "message": "invalid field values" or "details": [...]) indicating exactly which parameter failed validation.

When to Escalate

If you have verified that your JSON syntax is valid, your data types are correct, your headers are set properly, and a raw cURL request still fails with an uninformative 400 error message, the issue may stem from an undocumented API change or a temporary backend bug in Figma's parser.

Check the official Figma Status page to see if there are any active API or developer platform disruptions. If all services are operational, open a support ticket through your Figma developer account. Provide the full request payload (redacting sensitive API keys), the approximate timestamp of the failed call, and any response headers—especially the X-Figma-Trace-Id or correlation ID—to help developers locate the failure in their application logs.