request_overrides

Use request_overrides to stop selected network requests while Chrome renders an image. For example, you can prevent a third-party script or image from loading in a screenshot.

Pass an array of rules. Each rule currently supports the block action and must have a url pattern, a resource_types array, or both:

{
  "url": "https://example.com/report",
  "request_overrides": [
    {
      "action": "block",
      "url": "https://analytics.example.com/*",
      "resource_types": ["script", "xhr", "fetch"]
    }
  ]
}

url matches the full request URL. * matches any sequence of characters, including an empty sequence. Matching is case-sensitive. Without *, the pattern must match the entire URL exactly. For example, *://cdn.example.com/*.js matches JavaScript URLs on that host, while *.js matches only URLs ending in .js.

resource_types matches any listed browser resource type. Supported values are beacon, document, stylesheet, image, image_set, media, font, script, text_track, xhr, fetch, event_source, manifest, ping, img, and other.

When a rule has both url and resource_types, both must match. A request is blocked when any rule matches. A rule with only resource_types applies to matching requests from any URL. Blocking a document request can prevent the target page or an embedded frame from loading.

A page can make requests that add nothing to the image you want to capture. Blocking those requests can help you:

• Spend less time and bandwidth loading assets you won’t show. If a screenshot doesn’t need a video or a set of decorative images from your CDN, Chrome doesn’t need to download them for that render.
• Avoid sending screenshot visits to analytics services. Block tracking beacons or scripts when you don’t want automated renders counted alongside real visitors.
• Keep screenshots more consistent. Third-party chat widgets, ads, and other extras can change or fail independently of your page. Block them when they aren’t part of the image.

Only block resources your screenshot can do without. Blocking a font, stylesheet, script, or visible image may change the result.

To leave tracking beacons and a third-party chat widget out of a screenshot, use two rules. The first matches beacon requests from any URL; the second matches every request to the widget host:

{
  "request_overrides": [
    { "action": "block", "resource_types": ["beacon"] },
    { "action": "block", "url": "*://chat.example.com/*" }
  ]
}

If your page references CDN images that aren’t needed in the finished screenshot, block only that asset path. Other images on the page can still load:

{
  "request_overrides": [
    {
      "action": "block",
      "url": "*://cdn.example.com/unused-decorations/*",
      "resource_types": ["image", "image_set"]
    }
  ]
}

In a JSON image request, pass request_overrides as an array, as shown above. In an application/x-www-form-urlencoded request, send the entire array as one JSON-encoded field:

curl -X POST https://hcti.io/v1/image \
  -u 'UserID:APIKey' \
  --data-urlencode 'url=https://example.com/report' \
  --data-urlencode 'request_overrides=[{"action":"block","url":"*://cdn.example.com/*.js"}]'

The same JSON array or JSON-encoded form field can be supplied when creating or updating a template. Its rules apply when images are rendered from that template. You can also set default_options.request_overrides to a JSON array for an HTML/CSS OG configuration.

request_overrides is not supported in signed create-and-render query strings or hcti: page metadata tags.

• Up to 100 rules are allowed per request.
• Each url pattern can contain up to 512 characters and cannot contain control characters.
• Each rule must have action: "block" and at least one nonempty matcher. If supplied, url cannot be blank and resource_types cannot be empty.
• Each resource_types entry must be one of the supported names above.

Invalid rules return a request validation error.