← Image compressor

Compress an image with curl

Shrink an image for the web: lower quality, strip metadata, cap the width, or switch to WebP or AVIF. Here is the whole call with curl, with the output it produced when we ran it.

Before you start

An API key. Create a free account; it comes with free tokens every month. Put the key in an environment variable so it stays out of your code: export BLOODWEB_KEY=your_key
curl 7.76 or later (for --fail-with-body, which makes curl stop on an error and still show the reason).
The input file in the same folder: hero.png. Use your own; that is the name the code expects.

The code

Save it as image-compress.sh and run bash image-compress.sh.

curl -sS --fail-with-body \
  -H "Authorization: Bearer $BLOODWEB_KEY" \
  -F file=@hero.png \
  -F to=webp \
  -F quality=75 \
  https://bloodweb.net/api/v1/image-compress \
  -o hero.webp

What you get

Tested 19 October 2026: this exact code ran against our test copy of the API, which runs the same service code as bloodweb.net, and produced this.

It writes hero.webp: a WebP image, 1400 × 900 pixels, 10 KB.

Change the call

Every option the Image compressor takes. Add or change them the same way as the ones in the code.

quality: Lower is smaller. 70 to 80 is a good range for photos.
max_width: Shrink wider images to this width. Never enlarges.
to: Output format. Defaults to the input format (HEIC becomes JPG). One of: jpg, png, webp, avif, gif, tiff, bmp.
target_kb: Aim for a file no bigger than this many kilobytes. The highest quality that fits is used (JPG, WebP and AVIF). If even the lowest quality is too big, set max_width as well.
lossy_png: Reduce PNGs to 256 colours. Much smaller for graphics and screenshots; not for photos.

If it fails

A failed call is not charged. The answer is JSON with an error object; curl stops with an error, and that JSON lands in hero.webp instead of the result, so open it as text to read the reason. The usual ones:

401 missing_key or invalid_key: BLOODWEB_KEY is not set in the shell that runs the code, or the key was revoked.
415 unsupported_type: the file is not a type this service reads. The type is read from the file itself, so renaming a file does not change it.
413 file_too_large: the file is over the limit on the service page.
402 insufficient_tokens: the balance does not cover the call. Top up in the dashboard.
429 rate_limited: too many calls at once. Wait the seconds in the Retry-After header and send it again.

Every code and its fix is in the docs.

The Image compressor page: every option, the limits, and Try it now in your browser.
Getting started: keys, errors and rate limits for all the services.