Error Tracking

Send errors from a custom SDK with the error ingestion endpoint. Error tracking must be enabled for the project under Settings → Features before the collector accepts reports.

Endpoint

POST https://metrics.faststats.dev/v1/error
Authorization: Bearer <PROJECT_TOKEN>
Content-Type: application/json

The request body contains one or more errors and metadata shared by the batch:

{
	"language": "javascript",
	"identifier": "worker-01",
	"sessionId": "session-7d3f",
	"windowId": "request-42",
	"buildId": "2026.08.16",
	"sdkName": "acme-node",
	"sdkVersion": "1.4.0",
	"context": {
		"environment": "production",
		"region": "eu-central-1"
	},
	"errors": [
		{
			"error": "TypeError",
			"message": "Cannot read properties of undefined",
			"stack": [
				"TypeError: Cannot read properties of undefined",
				"    at handleRequest (/app/server.js:42:17)"
			],
			"handled": false,
			"count": 1,
			"context": {
				"route": "/checkout"
			}
		}
	]
}

Request fields

Batch fields

Field	Type	Required	Description
`errors`	array	yes	Error occurrences to ingest.
`language`	string	no	Stack-trace language. Defaults to `java`; see Supported languages.
`identifier`	string	no	Identifier for the affected installation, process, or user.
`sessionId`	string	no	Session associated with the errors.
`windowId`	string	no	Window or request associated with the errors.
`buildId`	string	no	Release/build identifier used to find an uploaded mapping file.
`context`	any JSON value	no	Structured metadata shared by every error in the request.
`sdkName`	string	no	Name of your SDK or integration.
`sdkVersion`	string	no	Version of your SDK or integration.

Error fields

Field	Type	Required	Description
`error`	string	yes	Error type or exception class, such as `TypeError` or `java.lang.RuntimeException`.
`message`	string	no	Human-readable error message.
`stack`	array of strings	no	Stack trace lines in their original order.
`handled`	boolean	no	Whether application code handled the error. Defaults to `false`.
`count`	integer	no	Number of identical occurrences represented by this item. Defaults to `1`; use a non-negative 32-bit integer.
`buildId`	string	no	Build identifier for this error. Overrides the batch-level `buildId`.
`context`	any JSON value	no	Metadata specific to this error. Object keys override matching batch context keys.

Keep stack frames as separate array entries. The collector joins them with newlines before grouping and applying source mappings.

Supported languages

The language controls stack-trace normalization, grouping, and mapping. Values are case-insensitive and surrounding whitespace is ignored.

If you need support for a language not listed here, please contact us.

Language	Accepted values	Mapping support
Java	`java`	ProGuard/R8 mappings
JavaScript	`javascript`, `js`	JavaScript source maps
PHP	`php`	None
Rust	`rust`, `rs`	None

If language is omitted or empty, the collector uses java for backward compatibility. Any other value returns 400 Bad Request:

{
	"error": "Unsupported language. Expected java, javascript, php, or rust"
}

Responses

A report accepted into the ingestion queue returns 200 OK:

{
	"status": "success"
}

The collector can also return:

Status	Meaning
`400 Bad Request`	The body is invalid JSON or `language` is unsupported.
`401 Unauthorized`	The authorization header is missing or the project token is invalid.
`403 Forbidden`	Error tracking is disabled or the request is blocked by the project’s IP rules.
`503 Service Unavailable`	The ingestion queue is full; retry the request with backoff.

Error responses have the shape { "error": "message" }.