Signed uploads

With signed uploads, you get to control who can and when can upload files to one of your Uploadcare projects. You need to generate a signature on your backend, and a trusted user should use this signature to upload a new file. It works with both File Uploader, jQuery widget, and Upload API.

Turning signed uploads on

Signed uploads can be turned on and off to an Uploadcare project, because it has a dedicated storage, Public and Private keys, and security settings.

  1. Go to your Dashboard and select an existing project or create a new one.
  2. Click Enable next to Signed Uploads in the uploading settings.

From now on, every request to Upload API should include a signature part. However, you'll still be able to upload files to your project via the Dashboard.

Signature generation

The signature string sent along with your upload request. To generate it, you need the secret key of your Uploadcare project, which you can get from the API keys section.

The signature is an HMAC/SHA256 with two parameters:

  • YOUR_SECRET_KEY — a generated key.
  • expire — an expiration time message (string).

Here's how to make the signature on your backend:

import { generateSecureSignature } from '@uploadcare/signed-uploads'

// by the expiration timestamp in milliseconds since the epoch
const { secureSignature, secureExpire } = generateSecureSignature('YOUR_SECRET_KEY', {
  expire: + 60 * 30 * 1000 // expire in 30 minutes

// by the expiration date
const { secureSignature, secureExpire } = generateSecureSignature('YOUR_SECRET_KEY', {
  expire: new Date("2099-01-01") // expire on 2099-01-01

// by the lifetime in milliseconds
const { secureSignature, secureExpire } = generateSecureSignature('YOUR_SECRET_KEY', {
  lifetime: 60 * 30 * 1000 // expire in 30 minutes


The expire string sets the expiration date and time or duration for a signature. It has a Unix time format.

The expire function in the Python example above adds a certain duration after the generation time. In this case, 30 minutes:

# Expire in 30 min, e.g., 1454903856
expire = int(time.time()) + 60 * 30

Signed upload example

To generate a signed upload, you need to pass 3 parameters:

  • YOUR_PUBLIC_KEY, which you can get from API keys
  • signature
  • expire


curl -F "YOUR_PUBLIC_KEY=caa9d29da887ee88ffe6" \
     -F "signature=46f70d2b4fb6196daeb2c16bf44a7f1e" \
     -F "expire=1454903856" \
     -F "" \


  "file": "c0d776d4-8c8e-47df-9e92-03b68b99c2ba"

To work with File Uploader, specify the secure signature and secure expire options.

To work with jQuery widget, specify respective secure signature and secure expire options.

Possible errors

Both signature and an active expire are required for every upload request and should be valid. The list of possible errors:

[HTTP 400] 'signature' is required.json
[HTTP 400] 'expire' is required.json

If expire is not a valid Unix timestamp:

[HTTP 400] 'expire' must be a UNIX timestamp.json

If your signature has expired, i.e., expire < now:

[HTTP 403] Expired signature.json

If signature is incorrect:

[HTTP 403] Invalid signature.json