How to Compress a PDF File Online (Free)

Large PDFs are a daily headache — too big to email, too big for the upload box on a job or exam portal. Here is how to shrink a PDF for free, without installing software and without uploading your file to anyone.

Last updated: June 2026

Why are PDFs so large?

A PDF's size is driven mostly by what is inside it. A text-only document is usually tiny. The moment a PDF contains scanned pages or photographs, its size balloons — a phone-scanned certificate can easily be 3–8 MB because each page is stored as a high-resolution image. That is why "compressing" a PDF really means reducing the resolution and quality of the images inside it.

How to compress a PDF in 4 steps

Open the Compressify PDF compressor.
Tap Choose a PDF and select your file.
Pick a level: Strong (smallest), Balanced, or Light (best quality).
Download the compressed PDF. The before/after size is shown so you know exactly how much you saved.

Open the PDF compressor →

Which compression level should I choose?

Level	Best for	Result
Strong	Tight limits (50–100 KB), scanned documents	Smallest file, softer text
Balanced	Most uploads (200–500 KB limits)	Good size/quality trade-off
Light	Email, when quality matters most	Crisp, moderate size reduction

Tip: compression is lossy, so start with Balanced, check the result, and only switch to Strong if you are still over the limit.

How to get a PDF under a specific size

Portals often demand an exact ceiling — 100 KB, 200 KB, 500 KB. Use these shortcuts, each pre-set for the target:

Under 50 KB Under 100 KB Under 200 KB Under 500 KB Under 1 MB

Tips for the smallest possible PDF

Scan in grayscale when colour isn't needed — it dramatically reduces size before you even compress.
Scan at 200–300 DPI, not higher. Ultra-high DPI adds size without helping readability on screen.
Remove blank pages and crop margins where possible.
Combine steps: a grayscale 200-DPI scan compressed on Balanced is usually enough for a 100–200 KB limit.

Is it safe to compress sensitive PDFs online?

With most websites, "online" means you upload your file to their server first — not ideal for certificates or ID documents. Compressify is different: it compresses the PDF entirely inside your browser, so the file never leaves your device. There is nothing to upload and nothing stored.

Frequently asked questions

Will compressing reduce the number of pages?

No. Every page is preserved — only the file size is reduced.

Will the text still be selectable?

Because pages are re-rendered as compressed images, the output is optimised for size and the text becomes part of the image. It stays clearly readable, which is what upload portals care about.

Does it work on a phone?

Yes. Compressify runs in any modern mobile browser, so you can compress straight from your phone.