Signed URLs

A signed URL is a link that renders an image or PDF when someone opens it. You make it once on your server, with your API key. Then you can put it anywhere: in an <img> tag, an email or an og:image tag. The link holds no API key, and nobody can change its values.

Create a signed URL

Send a render request to POST /v1/signed-urls. Nothing is rendered or charged yet.

curl https://api.jamframe.com/v1/signed-urls \
  -H "Authorization: Bearer $JAMFRAME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "templateId": "clx8m2k3p0001abcd1234efgh",
    "modifications": {
      "title": "How we cut render times in half",
      "author": "Jane Doe"
    },
    "response": { "format": "png" },
    "expiresIn": 2592000
  }'

const res = await fetch("https://api.jamframe.com/v1/signed-urls", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.JAMFRAME_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    templateId: "clx8m2k3p0001abcd1234efgh",
    modifications: {
      title: "How we cut render times in half",
      author: "Jane Doe",
    },
    response: { format: "png" },
    expiresIn: 2592000, // 30 days
  }),
});
const { data } = await res.json();
console.log(data.url);

import os
import requests

res = requests.post(
    "https://api.jamframe.com/v1/signed-urls",
    headers={"Authorization": f"Bearer {os.environ['JAMFRAME_API_KEY']}"},
    json={
        "templateId": "clx8m2k3p0001abcd1234efgh",
        "modifications": {
            "title": "How we cut render times in half",
            "author": "Jane Doe",
        },
        "response": {"format": "png"},
        "expiresIn": 2592000,  # 30 days
    },
)
print(res.json()["data"]["url"])

The answer:

{
  "data": {
    "url": "https://api.jamframe.com/r/s/cJa3HMV6TZzf.zPcqxCsIwFAXQXwnX….kDVEKgTbbJVl2AuLI64vRg.png",
    "templateId": "clx8m2k3p0001abcd1234efgh",
    "format": "png",
    "expiresAt": "2026-12-14T15:01:30.000Z"
  }
}

JamFrame checks the request as it would check a render. An unknown template is a 404, and a wrong value is a 400. Keys that match nothing come back in warnings.

The request

A signed URL can’t take async, webhookUrl, response.type, response.sizes, translate or ai. Those are a 400. If the link would be too long, that’s a 400 too: send fewer or shorter modifications.

Use the link

The link looks like https://api.jamframe.com/r/s/….png. It ends in .png, .jpg, .webp or .pdf, and is usually 200 to 300 characters long. Opening it answers with the file itself, so you can use it anywhere an image link works:

<img src="https://api.jamframe.com/r/s/cJa3HMV6TZzf.zPcq….png" alt="How we cut render times in half" />

<meta property="og:image" content="https://api.jamframe.com/r/s/cJa3HMV6TZzf.zPcq….png" />

• The values are part of the signature. Change any character and the link answers 403.
• After expiresIn, the link answers 410.
• JamFrame ignores anything after a ?, so tracking tags that email tools add don’t break the link.
• When something goes wrong, the link answers with a short JSON error, not a picture.
• Signed URLs don’t run AI. AI layers show their saved text and images.

Cache and credits

• The first visit renders the file. It costs credits like any render: 1 per image, or 1 per PDF page.
• Later visits within cacheSeconds get the same file from the cache. They’re free.
• Saving the template in the editor starts a fresh cache. The next visit renders the new version.
• Browsers and CDNs may keep their own copy for up to one day.
• HEAD requests never render and never cost anything.
• Each answer has an ETag. Send it back in If-None-Match to get a 304 when nothing changed. The X-Render-Cache header says HIT or MISS.

Limits

Anyone can open a signed URL, so it has tighter limits than the API. Requests and new renders have their own limits per minute, for each visitor, link and workspace. See Public links and forms.

When too many renders run at once, the link answers 503 with a Retry-After header. Try again after that many seconds.

Revoke all signed URLs

POST /v1/signed-urls/rotate-key gives your workspace a new signing secret. Every signed URL made before stops working at once and answers 403. Links you make afterwards use the new secret.

curl -X POST https://api.jamframe.com/v1/signed-urls/rotate-key \
  -H "Authorization: Bearer $JAMFRAME_API_KEY"

{ "data": { "rotatedAt": "2026-11-14T15:20:00.000Z" } }

• You can’t revoke one link on its own. To limit the risk, give links a shorter expiresIn.
• Browsers and CDNs may still show a copy they already have, for up to a day.
• Revoking an API key doesn’t stop the signed URLs it made. Rotate the signing key for that.

Errors when a link is opened

Signed URLs or dynamic URLs?

Both are public links that render when opened. They suit different jobs.

Use a signed URL when your server knows the values, such as a blog post’s title for its og:image. Use a dynamic URL when the values come from somewhere without an API key, such as an email tool’s merge tags. See Dynamic URLs.

Related

• The full render request: Render images and PDFs.
• Links you make in the app: Dynamic URLs.
• Every field: the Signed URLs endpoints in the API reference (opens in a new tab).