pdfviz

Compress PDF
to 4 MB

or drop one here
Compression level
Target size
Choose a PDF file first.

4 MB is 4,194,304 bytes. It is a comfortable cap for a document with photographs in it and a tight one for a long colour scan. The published bench did not run a 4 MB target, so this page quotes no measured hit rate for it, and says plainly what the image step costs when it runs and when it does not.

How to compress a PDF to 4 MB online

  1. Choose the PDF

    Press Choose a PDF, or drop the file on the page. The file is read in this browser tab and is not sent to any server.

  2. The target is already set

    This page opens with the target fixed at 4 MB, so there is nothing to type. Pick a different compression level if you want, or enter your own number in KB or MB for a different size.

  3. Press Compress

    Four methods race against each other: copy the pages into a fresh file, re-encode the placed images, cut each embedded font down to the glyphs the pages draw, and only when no other method reached the target, redraw the pages as images with the text kept on top.

  4. Read the check, then download

    Every candidate is opened again and its characters are counted against the source. The page shows the size, the method that won, and the characters kept before it offers the download.

The four methods are described in full, with the measurements behind them, in how it works. The whole process runs in your browser through WebAssembly, which means your file is never uploaded and no account is needed.

What the image step actually does at 4 MB

When the two lossless methods fall short, the engine re-encodes the page images. It picks a quality by sampling pages rather than guessing, walks down from high quality, and stops at the first setting that meets the target. It will not go below a fixed floor, because past that point the page stops being worth sending. That floor is what separates a free browser compressor from a slider that will happily ruin the file to hit a number.

The tool tells you the quality it picked, so you can decide whether the trade is acceptable before you download.

If the lossless methods reach 4 MB on their own, no image is re-encoded at all. The structural rebuild and the font subset leave every pixel untouched, and the output renders as sharp as the original at any zoom. The result names the winning method, so you know whether a pixel was touched.

What fits under a 4 MB cap

A thirty to forty page colour scan at a quality that still reads well. A brochure with a dozen product photographs. A hundred page text report with embedded diagrams. These are the documents where 4 MB is a realistic target that keeps the content usable.

What does not fit is a folder of full resolution phone photographs turned into a PDF. A single modern phone photo can be 4 MB before anything else is counted, so a photo album PDF needs a tighter target or fewer pages.

The compress tool tries the two lossless methods before it touches image quality, so a document that reaches 4 MB through a structural rebuild or a font subset renders as sharp as the original at any zoom. For photo heavy documents, the image method picks the quality that fits and tells you what it chose.

Choosing between 3 MB, 4 MB, and 5 MB

If the cap is a portal that stops at 3 MB, a 3 MB target is the right choice and gives up a third of the image budget. If the cap is the common 5 MB mail ceiling, a 5 MB target buys a quarter more image detail for the same effort.

If you are not sure which limit applies, 4 MB is a safe middle ground that clears most portal caps and most mail systems after encoding overhead. Mail inflates attachments by roughly a third, so a 4 MB file travels as about 5.3 MB, which clears a 10 MB mail limit easily but may bounce on a 5 MB one.

For the case where the source is far bigger than any of these numbers, the large file page covers where the real memory ceiling sits and what to do about it.

Real use cases for a 4 MB target

Portals with a 4 MB upload cap for brochures, catalogs, and product documentation. The image method keeps photographs usable at this budget.

Mail attachments sent through systems with a 5 MB or 10 MB limit. A 4 MB PDF travels safely after encoding on the larger limit and may need tightening for the smaller one.

Colour scans of thirty to forty pages. At roughly 100 KB per page, printed text and photographs stay clear and the file fits the common cap.

Questions about compressing a PDF to 4 MB

Does compressing to 4 MB reduce image quality?
Only if the two lossless methods fall short. The structural rebuild and the font subset run first and change nothing visible. If they reach 4 MB, no pixel is touched. If they do not, the image method picks the quality that fits and tells you what it chose.
What quality does the image step pick at 4 MB?
The tool samples pages rather than guessing and stops at the first setting that meets the target. It tells you the quality it picked, so you can decide whether the trade is acceptable before you download.
How many bytes is a 4 MB limit?
4,194,304 bytes in binary units. A portal counting in flat millions stops at 4,000,000, a gap of about 194 KB. If you have been refused once, target 3.9 MB to clear both readings.
Is 4 MB enough for a photo heavy brochure?
Usually yes, for a dozen or so photographs at a quality that keeps them usable. A folder of full resolution phone photos needs a tighter target or fewer pages, because a single phone photo can be 4 MB on its own.
Will the text stay selectable after compression to 4 MB?
Yes. Every candidate is re-opened and its characters are read back and compared with the source. Anything below 98% retention is refused.
Can I compress a 4 MB PDF on my phone?
Yes. Files this size are well inside what a phone browser handles. The compression runs in the tab exactly as it does on a desktop, and nothing is uploaded from either.

The other pdfviz tools

They all run in a browser tab like this one. Each reads its own output back and checks it before offering the download, and none of them needs an account.

Where to go next