Compress a PDF to Send on WhatsApp
On WhatsApp, a single document caps out at about 100MB — but the more common headache is that a large file is slow to upload and a recipient on mobile data won't download a 40MB PDF. Shrinking it with compress cat's Compress PDF makes it send reliably, faster, and lighter on the other person's data. Compression runs locally in your browser and nothing is uploaded. Below: WhatsApp's send limits and how to compress.
What are WhatsApp's limits for sending a PDF?
WhatsApp caps the size of a file sent as a document, and going over means it won't send; even under the cap, a large file slows your upload and the recipient's download.
- Sent as a document: roughly 100MB per file; over that it won't send.
- Upload / download speed: a tens-of-MB PDF is slow and data-hungry on mobile, so smaller is a better experience.
- Groups: the bigger the file, the more storage and data it costs every member — smaller is more considerate.
How do you shrink a PDF so it sends on WhatsApp?
Compressing on a computer and then sending works well, and so does opening compress cat in your phone's browser. Scans and photo PDFs compress best.
- Open Compress PDF and drag in the file you want to send.
- Set a target — for a fast, data-light send, try 5MB or 10MB.
- Click Start; compress cat binary-searches toward your target locally in your browser.
- Download, then send it on WhatsApp as a 'document'.
Will compression hurt the quality?
As long as you don't chase the smallest possible size, the key details survive. The contracts, receipts and document scans people send on WhatsApp are exactly the image-based PDFs compress cat handles best.
- Scans / photo PDFs: high ratio, great results — compress cat's strong suit.
- Pure-text documents: usually small already, so often no need; text becomes an image after compressing.
- Good enough beats tiny: the recipient just needs to read it, so 10MB is often safer than 2MB.
- Zoom in to check text and stamps after compressing, then send.
Frequently asked questions
WhatsApp says my PDF is too large — what do I do?
Compress it under the ~100MB document limit and it will send. If you just want it to send faster and lighter on data, set a smaller target like 5MB or 10MB. Compression runs locally in your browser, with nothing uploaded.
Can I compress a PDF on my phone before sending it on WhatsApp?
Yes. Open compress cat's Compress PDF in your phone browser, pick the file and a target, compress, download, then send it on WhatsApp as a document.
Will compression make it unreadable for the recipient?
Not if you don't overdo it. Set the target to 'good enough' rather than as small as possible. Scans and photo PDFs compress especially reliably — zoom in to check the key details before sending.
Is it safe to process the file in compress cat?
Yes. Compression runs entirely in your browser via WebAssembly, so the PDF is never uploaded and stays on your own device.
Updated · compress cat team