yiisoft/yii2 · error · NotAcceptableHttpException

The requested response format is not supported: $format

Error message

The requested response format is not supported: $format

What it means

Error "The requested response format is not supported: $format" thrown in yiisoft/yii2.

Source

Thrown at framework/filters/ContentNegotiator.php:196

     * @param Response $response
     * @throws BadRequestHttpException if an array received for GET parameter [[formatParam]].
     * @throws NotAcceptableHttpException if none of the requested content types is accepted.
     */
    protected function negotiateContentType($request, $response)
    {
        if (!empty($this->formatParam) && ($format = $request->get($this->formatParam)) !== null) {
            if (is_array($format)) {
                throw new BadRequestHttpException("Invalid data received for GET parameter '{$this->formatParam}'.");
            }

            if (in_array($format, $this->formats)) {
                $response->format = $format;
                $response->acceptMimeType = null;
                $response->acceptParams = [];
                return;
            }

            throw new NotAcceptableHttpException('The requested response format is not supported: ' . $format);
        }

        $types = $request->getAcceptableContentTypes();
        if (empty($types)) {
            $types['*/*'] = [];
        }

        foreach ($types as $type => $params) {
            if (isset($this->formats[$type])) {
                $response->format = $this->formats[$type];
                $response->acceptMimeType = $type;
                $response->acceptParams = $params;
                return;
            }
        }

        foreach ($this->formats as $type => $format) {
            $response->format = $format;

View on GitHub (pinned to 66f00d18a2)

When it happens

Trigger: Thrown at framework/filters/ContentNegotiator.php:196 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of yiisoft/yii2@66f00d18a2 (2026-08-17). Data as JSON: /api/errors/8fb75b03d87c1108. Report an issue: GitHub.