Will every PDF end up under 100 KB?

No. The tool lowers image quality level by level until the file fits, then returns the smallest result it reached. A file with little image content, or with image types that are skipped, can stay above the target.

Is 100 KB realistic for a multi-page PDF?

Seldom. Each page with an image needs its own share of the budget, and the strongest level caps images at 450 px on the long side. A long scan will usually return a smaller file that is still above 100 KB; Split by Page Count can send it in parts.

Does the text stay selectable?

Yes. Text, fonts and vector art are never changed. Image-only scans remain images.

What happens if my file is already under the limit?

It comes back with only the qpdf optimization applied and the content unchanged.

Can I use a different size?

Yes. Type any value from 0.05 to 1024 MB in the target field; the preset only saves you the typing.

Compress a PDF to Under 100 KB

Compress PDF to 100 KB repacks a PDF with qpdf and lowers image quality level by level until the file fits under 100 KB. If it cannot, you get the smallest result reached.

Drag and drop files here, or click to choose

Accepts PDF · up to 500.0 MB per file · up to 20 files at once

You can also paste a file with Ctrl/Cmd+V, or from the clipboard menu.

Target size in MB (optional)Leave empty for standard compression. Enter 1 to shrink the file to under 1 MB; the tool lowers image quality step by step until it fits.

Keep recent files in this browser (up to 5, 50.0 MB in total, never uploaded)

A 100 KB limit is the tightest size most upload forms ask for, and it is only realistic for short documents: a one-page form, a signed page, or a scan of a single certificate. The tool aims for it by shrinking the images inside the PDF, because images are where the bytes are.

The target field is already filled with 0.0976 MB. In this tool 1 MB is 1,048,576 bytes, so 0.0976 MB sits just under 100 KB. The tool first repacks the file with qpdf, then re-encodes page images as JPEG through up to seven levels, from quality 75 and a 2000 px longest side down to quality 18 and 450 px, and stops at the first result that fits.

Whether 100 KB is reachable depends on what the file holds. A page that is mostly photo or scan has room to shrink. A text-only PDF has no images to recompress, and since fonts are never subset or changed, a file that is already above 100 KB because of embedded fonts may stay above it. A multi-page scan is rarely reachable at this size.

Measured on freely licensed documents, the result depends on what the pages hold. Photographed JPEG pages shrink: a 32-page album went from 11.43 MB to 304.1 KB, the smallest it could make with a 100 KB target. Text and vector documents hardly change: a 15-page research paper went from 2.11 MB to 1.75 MB, the smallest it could make. Scans stored as JPEG 2000 or JBIG2 images, as many archive scans are, are skipped: a 38-page archive scan went from 2.23 MB to 2.22 MB, the smallest it could make. The table below lists every document.

The target is a goal, not a guarantee. If even the strongest level does not fit, you get the smallest result it reached, and the page count, page size, text and fonts are never changed. Image-only scans stay images, and 1-bit, CMYK, indexed, masked and transparent images are skipped, so a scan stored that way barely shrinks.

Image re-encoding is lossy. Open a few pages of the result before you send it, and keep the original. If a portal enforces a hard limit that the file cannot reach, Split by Page Count sends it in parts.

What happens at 100 KB: measured results

Document	Pages	Original	Result	Under 100 KB?
Attention Is All You Need (arXiv 1706.03762) (CC BY 4.0)	15	2.11 MB	1.75 MB	No
IRS Form 1040 (Public domain, US government)	2	215.1 KB	192.9 KB	No
Expedition 71 Crew Poster Brochure (NASA) (Public domain, NASA)	2	7.21 MB	93.5 KB	Yes
Album Or. 27.399, page 1 (Leiden University Libraries) (CC BY 4.0)	1	475.9 KB	51.0 KB	Yes
Album Or. 27.399, pages 1-5 (Leiden University Libraries) (CC BY 4.0)	5	1.41 MB	62.7 KB	Yes
Album Or. 27.399 (Leiden University Libraries) (CC BY 4.0)	32	11.43 MB	304.1 KB	No
Field letter (Internet Archive scan) (Public domain)	38	2.23 MB	2.22 MB	No

Measured on 2026-10-09 with this service's release build on freely licensed PDFs. KB and MB are 1,024 and 1,048,576 bytes. "Already under" means the original fit, so only the qpdf step ran. "No" rows show the smallest result the tool reached.

Features

Target size preset to 0.0976 MB (100 KB)
Seven image levels, JPEG quality 75 down to 18, longest side 2000 down to 450 px; stops at the first that fits
Page count, page size, text, fonts and vector art stay unchanged
Returns the smallest result reached if the target cannot be met
Anonymous API at /api/v1/misc/compress-pdf with targetSizeMb

When to use this tool

Fit a one-page signed form into a 100 KB upload field
Shrink a single scanned certificate or ID page
Send a one-page résumé from a photo-heavy template

How do I compress a PDF to 100 KB?

Upload the PDF that is over the limit.
Leave the target size at 0.0976 MB, or change it if the limit is different.
Click Process and download the result.
Check the file size against 100 KB and open a few pages to judge image quality.

Limits and edge cases

The target is a goal; the smallest result reached is returned
Strong levels make photos visibly softer
1-bit scans, CMYK, indexed, masked and transparent images are skipped
Does not subset fonts or convert color spaces
Password-protected files need the password first

Privacy for this tool

Files are uploaded over HTTPS, processed in memory or a short-lived temporary directory on our servers, and deleted when your result is ready. We do not keep copies for later browsing, training, or advertising profiles. See the Privacy Policy for retention details and AdSense cookie disclosures.

Frequently asked questions

Will every PDF end up under 100 KB?: No. The tool lowers image quality level by level until the file fits, then returns the smallest result it reached. A file with little image content, or with image types that are skipped, can stay above the target.
Is 100 KB realistic for a multi-page PDF?: Seldom. Each page with an image needs its own share of the budget, and the strongest level caps images at 450 px on the long side. A long scan will usually return a smaller file that is still above 100 KB; Split by Page Count can send it in parts.
Does the text stay selectable?: Yes. Text, fonts and vector art are never changed. Image-only scans remain images.
What happens if my file is already under the limit?: It comes back with only the qpdf optimization applied and the content unchanged.
Can I use a different size?: Yes. Type any value from 0.05 to 1024 MB in the target field; the preset only saves you the typing.

Last updated: 2026-10-09

Call this from code

Every tool on this site is a plain REST endpoint - no account or API key needed for anonymous use. Built for AI agents and developers as much as for browsers.

curl -X POST "https://pdf123.xyz/api/v1/misc/compress-pdf" \
  -F "[email protected]" \
  -o output.pdf

Also available as an MCP tool for agent clients that speak Model Context Protocol (JSON-RPC 2.0 over POST /mcp). Full API reference

Use it from an AI agent

Skill

Claude Code, Codex, Cursor and other AI agents can run Compress for you with this skill: /skills/pdf123-compress.md

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Files are used only for this processing job and deleted automatically afterward.