How do I compress a PDF?
- 1Choose your PDF, or drag it onto the box. If it has a password, type it to open the file.
- 2Pick Balanced, Strong, or Target size and the limit you need, such as 200 KB.
- 3Press Compress PDF and wait while each page is redrawn.
- 4Check the new size and download the compressed PDF.
How does PDF compression work?
- 01Each page → a JPEG picture at the chosen DPI and quality → a new PDF at the original page size
- 02Picture pixels = page width (in) × DPI × page height (in) × DPI
- 03Balanced = 150 DPI, quality 75 % · Strong = 100 DPI, quality 60 %
- 04Target size: lower DPI and quality step by step until the file is under the limit (1 KB = 1000 bytes)
Scans and phone photos of documents are big because every page is a large, detailed picture. This tool redraws each page as a smaller JPEG picture and builds a new PDF from them, with every page at its original size. Going from 300 DPI to 150 DPI keeps a quarter of the pixels, so the file often shrinks by 70–90 %.
JPEG quality decides how much fine detail is kept: around 75 % looks clean on screen, and lower values make smaller files with softer edges. For a target size, the tool tries the sharpest setting first, measures the real file, and steps down DPI and quality until the PDF fits — so you get the best quality under your limit. 1 KB is taken as 1000 bytes, so the file also passes forms that count 1 KB as 1024 bytes.
Be aware of the trade-off: the pages become pictures, so text can no longer be selected or searched, and links, bookmarks and form fields are dropped. A PDF made from text (for example exported from Word) is usually already small and may even get bigger — in that case the tool tells you to keep the original.
Pages are drawn with Mozilla's pdf.js and the new file is built with pdf-lib, both running entirely on your device. Nothing is uploaded.
Good to know
- An upload form says 200 KB or 1 MB? Use Target size — the tool picks the sharpest version under that limit.
- Scanning a document? Scan at 150–200 DPI in colour only if you need colour — it starts the file much smaller.
- Remove blank or unneeded pages with Split PDF first; fewer pages means a smaller file.
- Keep your original PDF: the compressed copy has pictures of the text, not the text itself.
Compress PDF — common questions
Is my PDF uploaded to a server?
No. The PDF is opened, redrawn and rebuilt in your browser on your own device. Nothing is sent anywhere.
How do I compress a PDF to 200 KB or 100 KB?
Choose Target size and pick 200 KB or 100 KB (or type your own). The tool lowers the picture quality step by step until the file is under the limit, keeping it as sharp as possible.
Will the text still be selectable?
No. Each page becomes a picture, so text can't be selected, copied or searched, and links and form fields are removed. That's why this tool is best for scans and photos of documents.
Why did my PDF not get smaller?
PDFs made from text (for example saved from Word) are already small, and turning their pages into pictures can make them bigger. When that happens the tool says so and you should keep the original.
Can I compress a password-protected PDF?
Yes. Type the password to open it; it is used only on your device. The compressed copy is saved without a password.
What if it can't reach my target size?
Very long documents may not fit a small limit while staying readable. The tool shows the smallest size it could make; remove pages you don't need with Split PDF and try again.
Sources
- Mozilla pdf.js — the open-source PDF renderer used here
- pdf-lib — create and modify PDF documents in JavaScript
- PDF Association — about the PDF format (ISO 32000)
Formulas last reviewed: September 30, 2026 ·How we check our formulas