How to compress a PDF in your browser: Standard vs Maximum mode, JPEG quality and DPI options explained
A PDF that is too large to email, upload or share is one of the most common document problems — and the fix depends on what is making the file heavy in the first place. Photos and scans dominate file size; text barely registers.
This guide is the practical companion to the Compress PDF tool: what each option does, which mode to pick, how to tune the advanced settings, and what honest results look like. The tool runs entirely in your browser, so your file never leaves your device.
Before you start: what is making your PDF large?
Compression works on what is already inside the file, so the biggest lever is understanding the content:
- Image-heavy PDFs (scans, photos, presentations with full-bleed pictures) — these shrink dramatically in Maximum mode, because the images are re-encoded at a smaller quality and resolution.
- Text-only PDFs (exported from Word, generated reports) — already compact. Expect a modest reduction in Standard mode and little benefit from Maximum, which would rasterize clean text into images and make the file bigger.
- Mixed documents — Standard mode handles the text cleanly and the tool keeps everything selectable; Maximum is the choice when the smallest possible file matters more than searchability.
Step by step: compress a PDF
- Open the Compress PDF tool and upload your PDF (up to 100 MB).
- Choose a compression level: Standard (keeps selectable text) or Maximum (smallest size).
- Optional: open Advanced options to set JPEG quality and render DPI for Maximum mode.
- Click Process and watch the progress bar — processing is local, so it runs as fast as your device allows.
- Compare the new size against the original on the result screen.
- Download the compressed PDF, or process again with different settings and compare.
Standard vs Maximum: the real difference
| Standard | Maximum | |
|---|---|---|
| What changes | Cleans redundant structure, re-encodes streams | Rasterizes every page into a compressed JPEG image |
| Text stays selectable | Yes — searchable and copyable | No — the text layer is replaced by the page image |
| Size reduction | Moderate, content-dependent | Largest, especially for scans and photos |
| Best for | Contracts, reports, documents people search or quote | Emailing scans, photos and image-heavy files |
The choice is a trade-off between size and usefulness. If a recipient will search, quote or edit the document, keep Standard. If the file only needs to be readable — a scan being emailed, a photo album being uploaded — Maximum gives the smallest honest result.
Tuning Maximum mode: quality and DPI
Maximum mode has two advanced controls that let you balance size against visual detail:
- JPEG quality (0.3–0.95, default 0.7) — lower values produce smaller files with softer images. 0.7 is a safe middle ground; drop toward 0.5 for email-sized files, raise toward 0.9 for images people will zoom into.
- Render DPI (72–300, default 144) — the resolution pages are rasterized at. 144 DPI looks sharp on screen and prints acceptably; 300 DPI keeps fine detail for print but multiplies the file size.
These two controls are the entire size story for Maximum mode: halving the DPI quarters the pixel count, and lowering JPEG quality shrinks each image further. Start with the defaults, then tune one direction at a time and compare the reported sizes.
What the result screen tells you
After processing, the tool shows the original and compressed sizes side by side, and verifies the output is a valid PDF before offering the download. Use that comparison to decide whether the current settings are right: if the reduction is small, the file was probably text-heavy (normal), and if the visual quality dropped more than you like, raise quality or DPI and run it again.
Common mistakes and how to avoid them
- Using Maximum on a document that must stay editable — the text layer is gone; run Standard instead.
- Compressing the same file repeatedly — each pass re-encodes the previous result and gains almost nothing while risking image degradation. Always compress from the original.
- Expecting a fixed percentage — image-heavy PDFs shrink far more than text PDFs. Any promise of a guaranteed ratio is oversimplification.
- Forgetting the advanced controls — for Maximum mode, quality and DPI are where the real size savings live; the defaults are good but not optimal for every document.
Troubleshooting
The compressed PDF is still large
Most likely the file is text-only (little to remove) or the images dominate and Standard mode left them intact. Try Maximum mode, and lower JPEG quality or DPI in Advanced options if the file is still heavy.
Text is no longer selectable after processing
You used Maximum mode — it rasterizes pages by design. Re-run with Standard mode if selectable text matters.
The output looks blurry or soft
Maximum mode with low quality or DPI sacrifices detail. Raise quality toward 0.85 or DPI toward 200 and compare — the before/after sizes will tell you what you gained for the quality you kept.
The tool reports an error with my file
The file may be corrupted or use unsupported features. Verify it opens in a normal PDF reader, then try a fresh copy. Since processing is local, there is no server-side copy to worry about.
Privacy and limits
Compression is 100% client-side: the PDF is read, re-encoded and written inside your browser tab, and the bytes never leave your device. That makes the tool safe for confidential documents — no upload, no server copy, nothing to retain or delete.
- File limit: 100 MB per PDF — a browser-memory limit, not a paywall.
- No guaranteed compression ratio — results depend entirely on document content.
- Maximum mode removes the text layer; keep the original if you may need searchable text later.
- Rasterizing many pages at high DPI is compute-heavy — very large Maximum jobs can take a while on modest hardware.