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PDF Compressor

Compress a PDF, compare file sizes, and download.

Runs locally · Nothing is uploaded

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Worked example · Evaluate compression instead of promising a target size

Worked example

Evaluate compression instead of promising a target size

Use a non-sensitive scanned PDF and a text PDF as separate trials. They contain different kinds of data, so they need not shrink by the same amount. Always keep the originals: a smaller file is useful only if its content is still fit for the recipient.

Input and settings
Scanned PDF or text PDF · original retained
Expected output
Measured result · smaller size is not guaranteed

Steps to reproduce

Try the appropriate available compression mode. Read its loss and compatibility notice before running, then compare the reported input and output bytes. Review the result instead of immediately replacing the source.

Check before you use it

Open pages containing fine print, diagrams and signatures. Where a mode rasterizes pages, searchable text and interactive features may not survive. If the output is too large or loses needed features, retain the original, change the mode or use the PDF Submission workflow to evaluate a specific delivery requirement.

How PDF Compressor works, privacy, and related tools

Task path / input to outcome

How to compress a PDF

  1. 01

    Choose one PDF

    Select Choose one PDF and open a document of up to 30 MiB with at most 500 pages. The file opens inside this tab; nothing is uploaded, and an encrypted or corrupt document is refused with a clear message instead of a hung run.

  2. 02

    Pick a compression mode

    Choose structure optimization to keep text, or allow strong compression to turn pages into images. In target mode, structural optimization always runs first; image candidates require Strong compression.

  3. 03

    Compress to a size target

    Enter 0.1–30 MiB, with up to two decimal places. No thousands separators. Target mode uses fixed candidate settings; the manual quality slider does not apply. Structural optimization runs first. If you allow image pages and the target is still missed, try up to four JPEG settings (85%, 75%, 65%, 55%) at 150 DPI. The search has a 60-second cancellation budget; an active engine call may take longer to stop. Size is not a readability score. Intermediate PDFs are capped at 30 MiB; this is not a limit on total browser memory.

  4. 04

    Set the JPEG quality

    In manual Strong compression, JPEG quality ranges from 0.3 to 0.9 in steps of 0.05, initially 0.7. Pages render at 150 DPI and text is no longer selectable or searchable. Output size depends on the source and browser. Target mode uses fixed candidates instead of this slider.

  5. 05

    Compress and compare

    Press Compress PDF and check the before-and-after sizes with the reduction percentage rounded to one decimal. If the result is the same size or larger, the tool says so plainly — zero for the same size, negative if larger — and still lets you download it; the file is named after yours with -compressed appended. Long rasterize runs report per-page progress as they go.

Tool facts

Processing
In your browser
Input leaves this device
Never
Retention
Nothing is stored
Price
Free

Your input stays in the browser.

PDF Compressor uses its verified local execution path and does not create a hidden input or output history.

Local execution

Runs inside the current browser tab.

No hidden processing

Active tool data never becomes a Toolars document record.

No account required

Use the core workflow without creating a profile. Favorites sync to your account after you sign in.

Immediate reset

Clear the tab and the active working data is gone.

When PDF Compressor is useful

Keep text selectable

Open a text PDF and choose Optimize structure. Compress, download, and check that you can still select text. Compare the measured byte sizes; a smaller file is not guaranteed.

Prepare a 2 MB attachment

If the portal means 2,000,000 bytes, try a 1.90 MiB target. Keep structure mode when text must remain selectable. Check the downloaded size and readability; reaching the target does not guarantee portal acceptance.

Fix an invalid target

A target of 0.09 MiB is below the allowed range. Replace it with 1.90 and run again. If the result misses the target, review the best completed output or revise the source document.

What PDF Compressor actually does

For a portal attachment limit, enter its byte goal and choose whether text must remain selectable. Compare the actual output with the limit. If allowed candidates cannot reach it, download the best completed result or revise the document; changing quality does not guarantee success.

Common questions

What is the difference between the two modes?
Optimize structure clears the PDF Info dictionary and rewrites the file structure; text stays selectable and searchable, but embedded images keep their original encoding. Strong compression re-renders every page as a 150 DPI JPEG at the quality you choose. It may reduce an image-heavy file, but the result can also be larger; page text becomes a bitmap.
Why did Optimize structure barely shrink my file?
That mode clears the PDF Info dictionary and rewrites the structure; embedded images keep their original encoding. Strong compression re-renders pages as JPEGs and may reduce their size, but the result is not guaranteed to be smaller. Check the measured before-and-after sizes and the downloaded document's readability.
What does the quality slider do?
In manual Strong compression, JPEG quality ranges from 0.3 to 0.9 in steps of 0.05, initially 0.7. Pages render at 150 DPI and text is no longer selectable or searchable. Output size depends on the source and browser. Target mode uses fixed candidates instead of this slider.
Will I lose the ability to select and search text?
Strong compression turns pages into bitmap images at 150 DPI, so an existing text layer can no longer be selected or searched; the workspace discloses this before you run it. Optimize structure does not rasterize text, but it cannot add a text layer to a scan that never had one. Check the downloaded result.
Can I compress an encrypted or corrupt PDF?
No. A document the engine cannot open — encrypted, password-protected, or structurally broken — is rejected with a clear message that says so, in both modes. Remove the password with the tool that issued it, then compress the decrypted file here.
Can I choose a target file size?
Enter 0.1–30 MiB, with up to two decimal places. No thousands separators. Target mode uses fixed candidate settings; the manual quality slider does not apply. Structural optimization runs first. If you allow image pages and the target is still missed, try up to four JPEG settings (85%, 75%, 65%, 55%) at 150 DPI. The search has a 60-second cancellation budget; an active engine call may take longer to stop. Size is not a readability score. Intermediate PDFs are capped at 30 MiB; this is not a limit on total browser memory.
A portal allows 2 MB. Should I enter 2 MiB?
No. If the portal means 2,000,000 bytes, 2 MiB is larger at 2,097,152 bytes. A 1.90 MiB target leaves a small margin, but confirm the actual output bytes and the portal rules. Inspect small text and keep the original: reaching a size target does not prove readability or acceptance.

Keep reading

Continue in PDF Tools

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Move into another focused workspace without returning to the full index.

PDF Splitter

Extract selected pages or ranges into one new PDF, in the order you choose. Files stay in your browser and the original is unchanged.

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PDF Page Organizer

Reorder, delete, or extract PDF pages from a keyboard-operable thumbnail grid, and download the result without touching the original.

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PDF Merger

Merge 2-12 PDFs in your chosen order — up to 50 MiB and 500 pages combined — entirely in the browser, with per-file validation.

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PDF Metadata Remover

Inspect and clear PDF Info fields — Title, Author, Creator, and more — with optional XMP removal, verified after saving, locally.

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