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// api reference

Compress PDF API

Reduce PDF file size by up to 70% without a noticeable loss in quality. Perfect for faster uploads, email attachments, and saving storage.

The functionCalling itOther PDF tools

How it works

Every PDF tool runs as a small CustomJS function using our built-in pdfUtils. Write a few lines of JavaScript, deploy once, and you get a private API endpoint you can call from anywhere. Make.com, n8n, or plain curl.

01

Paste the function below into the editor at app.customjs.space.

02

Set the Response Type to PDF and deploy.

03

Call your function URL with the x-api-key header.

The CustomJS function

Import PDF_COMPRESS from ./utils and return its result. Remember to set the function's Response Type · PDF

const { PDF_COMPRESS } = require('./utils');

const pdfInput = input.url || input.file;

return PDF_COMPRESS(pdfInput);

Calling your endpoint

POST to your function URL. Pass the source PDF either as a public URL or a Base64 string. The request payload is capped at 6 MB.

Request body

FieldTypeDescription
urlstringPublic URL of the source PDF. Provide either url or file.
filestringBase64-encoded PDF binary (payload max 6 MB).

Example. Source from a URL

curl -X POST https://e.customjs.io/<your-function-id> \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "url": "https://css4.pub/2017/newsletter/drylab.pdf"
  }' --output compressed.pdf

Example. Source as Base64

curl -X POST https://e.customjs.io/<your-function-id> \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "file": "JVBERi0x..........EyNzg3CiUlRU9GCg=="
  }' --output compressed.pdf

Other PDF tools

HTML to PDF

Render HTML & templates to PDF

PDF to PNG

Pages to high-res images

PDF to Text

Extract plain text

Merge PDFs

Combine files into one

Extract Pages

Pull selected pages

// try it first

Prefer to play before you code?

Open the interactive playground on the product page. Generate PDFs live, tweak the code, and copy the generated curl or SDK snippet straight into your stack.

Open the playground Get an API key
compress-pdf.curl
curl -X POST https://e.customjs.io/<your-function-id> \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{
    "url": "https://css4.pub/2017/newsletter/drylab.pdf"
  }' --output compressed.pdf

600 free operations / month · no credit card

Frequently Asked Questions