Compress PDF Files Online

Free Online PDF Compressor

Free online PDF compressor reduces PDF file size with three profiles, Low, Medium or High Quality, none behind a paid tier. Select one, click Compress PDF and download the smaller file.

PDF tooling by OnlinePCApps since 2013

Runs on device No sign-in Every level free Three profiles
0
Bytes leaving
3
Quality profiles free
∞
Documents per day
$0
Cost, permanently
Where a size limit applies

Online PDF Compressor for Email, Portal and Storage Limits

Compress PDF files online when a mailbox, a portal or a shared drive sets a ceiling the document overshoots. Every limit is imposed elsewhere rather than a defect in the PDF.

Attachment Limits

Gmail and Outlook reject attachments above roughly 25 MB. A scanned contract or a slide deck exported to PDF passes that figure without difficulty.

Online PDF compressor shrinks the document with one of three profiles. Low Quality in the PDF compressor gives the smallest file for a mailbox limit.

Fixed Ceilings on Submission Portals

Government portals, job applications, visa forms and academic submissions routinely specify an exact figure: 100 KB, 200 KB, 500 KB or 1 MB, enforced by rejection rather than a warning.

There is no target-size field. Select Low Quality for the smallest output, then check the file size before submitting.

Storage and Distribution

Document archives and shared drives accumulate invoices and scans held at capture resolution rather than reading resolution.

The PDF compressor applies one profile across the document and leaves text and structure untouched.
How it works

Compress PDF Files Online in Three Steps

instant PDF

Upload the PDF

Drop one PDF, 100 MB at most, onto the online PDF compressor panel above or browse for it. The file card shows the size and Ready to compress.

instant

Select a Compression Profile

Three profiles in the PDF compressor: Low Quality for the smallest file, Medium Quality for the balanced default or High Quality for the best visual result.

instant

Compress and Download

Compress PDF starts the run and Download compressed PDF ends it. The file is saved under compressed_ plus the source name and the original stays untouched.

Three profiles Low, Medium and High Quality, none paywalled
Medium by default Balanced compression, recommended
Predictable name Saved under compressed_ plus the source name
Compress a PDF Free, nothing to register The Desktop Build For directory-level runs
Against the category

Online PDF Compressor vs a Hosted Compressor

Several well-known compressors keep the stronger levels for a paid plan and meter free runs per day. Row by row, here is where the online PDF compressor on this page differs.

This page This compressor Runs on local hardware A typical server-side compressor Sends the document to a server
Compression levels at no cost All three Basic only, 20 to 40 percent
Strongest level at no cost Yes, Low Quality Often a paid feature
Page count limit None 200 pages on some free tiers
Where the rewrite happens This machine A remote datacentre
Runs allowed per period Unmetered Two or three per day or hour
Largest file accepted 100 MB per file 10 MB on some free tiers, 2 GB on one
Copy held afterwards None exists Purged after one to twenty-four hours
Confidential material No restriction Subject to their policy
Effect of geography None Throughput falls with distance

That describes how the category generally operates and singles out no particular service. Column one is what the online PDF compressor on this page does.

Compressor data handling

PDF Compressor Privacy and Data Handling

Deletion timers are the standard reassurance here. One hour is typical, and the guarantee extends only as far as the operator's practices allow.

No timer applies where no document arrives. There is no endpoint capable of receiving a document and nothing of ours executes remotely. Open the browser developer tools, watch the network panel during a run and it stays empty throughout.

$ Network panel while compressing a 90 MB scan
→ external requests ....... 0
→ source document ....... 0 requests
0
Bytes leaving
0
Sign-ups
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Copies kept
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Third-party scripts
Compression mechanism

What the Online PDF Compressor Removes and Rewrites

The PDF compressor rewrites a document so it occupies less space: images resampled, fonts subset, redundant objects dropped. The table sets out every element, and what conversion loses covers the trade.

ElementEffectDetail
Colour imagesdownsampled and re-encodedResolution is reduced to the level the profile sets, then the image is re-encoded as JPEG. This accounts for most of the reduction the PDF compressor gets on a scanned document.
Greyscale imagesdownsampled and re-encodedHandled the same way as colour, at the same profile level. Scans of printed text sit here rather than in the colour path.
Monochrome imagesdownsampled onlyBitonal scans are resampled but kept in a lossless CCITT or JBIG2 encoding, because JPEG artefacts are conspicuous on line art.
Image resolutionset by profileLow Quality resamples hardest, High Quality keeps the most detail and Medium Quality sits between. The online PDF compressor exposes the three profiles, not a DPI field.
Embedded fontssubsetOnly the glyphs the document uses are retained. A font embedded in full can carry thousands of unused characters.
Duplicate objectsmergedDeduplication in the PDF compressor means a logo repeated on forty pages is stored once and referenced forty times rather than embedded forty times.
Unused objectsdiscardedOrphaned dictionary entries left by earlier edits are removed and the cross-reference table is rebuilt. These accumulate quietly through repeated saves.
Page thumbnailsremovedCached preview images are regenerated by any reader on demand, so the PDF compressor drops them.
Document metadataretainedTitle, author and keyword fields are kept. They occupy a negligible amount of space and removing them serves no purpose.
Text contentuntouchedText lives in the content stream as drawing instructions rather than pixels and is already compact. It is never rasterised or degraded.
Vector artworkuntouchedLine art, charts and logos drawn as vectors stay vector. Converting them to images would increase size, not reduce it.
Form fieldsretainedAcroForm fields and their values survive compression, so a filled form stays fillable.

Where the behaviour is defined

ISO maintains PDF as an open standard. Compression reaches into the image dictionaries, the font descriptors and the object table, all of which the sources below define.

ISO 32000-1 Defines image XObjects, the filter chains that encode them and the font descriptor entries that subsetting rewrites. PDF 1.7 reference Published free of charge by Adobe by agreement with ISO, filter definitions and all. ITU-T T.81 The JPEG specification, published jointly as ISO/IEC 10918-1. Describes the discrete cosine transform and quantisation that make image re-encoding lossy and cumulative. Library of Congress Written for digital archives. Sets out which parts of a document must survive for it to remain openable decades later.

Object structure is described in the PDF specification, which defines the indirect references that allow a repeated logo to be stored once. What a PDF keeps after an edit or redaction shows why a compressed file can still carry more than the page displays.

What to expect

PDF Compressor Results by Document Type

Results from the PDF compressor vary by an order of magnitude with the input. The four cases below cover almost every document brought to it, with the profile to select for every one.

Scanned Documents

A page scanned at 600 dpi carries roughly four times the data a 300 dpi page needs for the same legibility.
Reductions of 80 to 90 percent are ordinary here because the input was over-resolved to begin with.
Note: Low Quality can leave small print soft. Open a page of body text in the compressed file before sending it.

Photographic Content

Photographs and screenshots re-encode well in the PDF compressor and account for most of the size in a presentation exported to PDF.
Typical reduction runs from 50 to 80 percent depending on the original encoding.
Note: Repeated JPEG re-encoding compounds. Compressing an already compressed document degrades images for very little gain.

Text-Only Documents

A contract or report with no images is already close to its minimum size.
Expect single-digit percentages from font subsetting and object cleanup rather than a dramatic drop, which how a PDF stores text explains.
Note: A tool promising 90 percent on a text-only PDF is either rasterising the pages or reporting a different file.

Already Optimised Files

A document compressed once has had its images downsampled and its objects cleaned already.
A second pass returns very little and costs image quality every time.
Note: Where a file will not shrink further, the reason is that there is nothing left to remove, not that the PDF compressor failed.

Compress Before Merging

Note that one pass and smaller inputs produce a better result than compressing a file from the online PDF merger afterwards, because every source is optimised at its own resolution.

Compressing after a merge applies one setting to every source, including the pages that did not need it.

Encrypted and Signed Files

Note that a password and a signature both block the operation for different reasons: one prevents reading, the other cannot survive a rewrite.

Remove the restriction with the online PDF unlocker before compressing, and apply any signature to the compressed result rather than the original.
Desktop edition

Desktop PDF Compressor for Entire Folders

The online PDF compressor takes one PDF up to 100 MB per run. Running a folder of scans through one profile is desktop-build territory.

Where the Desktop Build Fits

The PDF compressor takes one file per run and checks it against a 100 MB cap. A long scan within that cap presents no difficulty.

Working page by page straight off the disk is what the desktop build does, and that removes the memory question.

Online compressor100 MB per file
Desktop toolbounded by free disk
Never connects

Nothing reaches the network once installed, which suits controlled estates and offline workstations.

No memory ceiling

Pages are read from disk one at a time instead of being held together, so length stops mattering.

Folder-level batches

Apply one resolution target across a directory in a single pass.

Built for repeat work

Entire directories handled at one resolution target, beyond what one tab can hold.

Saved profiles

Store a level and a target, then apply the same settings to future documents.

Runs disconnected

Requires no network access at all once set up.

About the Desktop Build Trial version · Windows 10 upward $39 outright · nothing recurring · refundable within 30 days
Reference

Online PDF Compressor Questions

The online PDF compressor reduces the size of a PDF with one of three profiles. You upload the file, select Low, Medium or High Quality and click Compress PDF. The download is named compressed_ plus the source file name, with no account and no profile held behind a paid tier.
That depends almost entirely on what your document contains. Scanned pages commonly reduce by 80 to 90 percent because scanner output is captured at a far higher resolution than reading requires. Photographic content typically drops by 50 to 80 percent. A text-only report may reduce by only a few percent, because text is stored as drawing instructions and is already compact.
Because there was little to remove. Text and vector artwork occupy very little space, so a document containing only those is already near its minimum. A file that has been compressed once has also had its images downsampled already. In both cases the absence of a reduction points to an efficient file rather than a failure of the PDF compressor.
Yes. Low, Medium and High Quality are all available for your file without an account. Some providers reserve their stronger levels for a paid tier, which leaves the free option unable to reach the sizes people generally need.
Not on this page. There is no target-size field. Select Low Quality for the smallest output and check the size of the download. If it is still over, split the document with the online PDF splitter and compress the parts.
Select Low Quality and compress. Whether 100 KB is reachable depends on the content: a text-only document usually lands well under it, while a multi-page colour scan may not at any profile that keeps the text legible. Check the size of your compressed_ file before submitting it.
100 KB and 200 KB are the most common for identity documents and application forms. 500 KB and 1 MB appear on academic and tender portals that accept multi-page submissions. 2 MB and above are typical of job application systems accepting a full document set. Select Low Quality in the PDF compressor and check the result against the figure.
No. Both the analysis and the rewrite occur inside the browser, on whichever machine holds the file. Nothing here can take delivery of a document. Open the browser tools and the network view stays silent for the entire run.
No. Text is stored as instructions referencing an embedded font rather than as pixels, so it is neither rasterised nor re-encoded. Text in your compressed document remains selectable, searchable and as sharp as the original.
Every font is subset so that only the glyphs the document uses are retained. A font embedded in full can carry several thousand characters for a document that uses eighty. Appearance is unchanged because the glyphs in use are the ones kept.
Low Quality gives the smallest file and resamples images hardest. High Quality keeps the most image detail for the least reduction. Medium Quality is the recommended default of the PDF compressor and balances the two for your document.
At High Quality, yes, because it keeps the most image detail. Low and Medium Quality are intended for viewing and for email, and printing from them shows visible softening in photographs. Run High Quality when your output is headed for a printer.
Scans respond better than any other input. A page captured at 600 dpi holds roughly four times the data that 300 dpi requires for the same legibility, so the surplus is removed without affecting readability. Check small print before accepting Low Quality.
It can, but the second pass returns very little. Images have already been downsampled and re-encoded, and repeating JPEG encoding compounds its artefacts. Compressing once at the right PDF compressor profile produces a better result than compressing twice at a mild one.
Yes. Interactive fields and any values entered in them survive the online PDF compressor, so your filled form remains fillable and its data intact.
No. The PDF compressor rewrites the file, and a signature certifies one exact byte sequence. The field remains but no longer validates. Compress first and sign your result.
No, an encrypted document cannot be read until the password is gone, and a file with owner restrictions may open normally yet still refuse the extraction step compression depends on. Strip the password with the online PDF unlocker and send the unlocked copy to the PDF compressor.
Yes, 100 MB per file on the online PDF compressor. A heavier file is refused with a message when you add it. Split it first with the online PDF splitter, compress the parts and merge them again.
No. No watermark, no daily allowance and no trial window are applied by the online PDF compressor. Your download holds the compressed document by itself.
Yes. Chrome, Firefox, Safari and Edge run it on Windows, macOS, Linux and ChromeOS. The page loads on your Android or iOS device too, and nothing is installed anywhere.
A static page whose work happens on the visitor's own hardware costs almost nothing to host, and no document is ever received, processed or stored at this end. The desktop edition, bought by people running directory-level and oversized jobs, pays for the browser tools.
No. The PDF compressor writes the compressed document to a separate file named compressed_ plus the source name, so the original remains available if the result is not acceptable.
More apps

More Tools to Work With PDF Files

Nothing below needs an install. Once the online PDF compressor has done its part, the smaller file can be merged, split, reordered or locked in the same tab.

Merge PDF
Online PDF merger to combine documents into one file.
Split PDF
Online PDF splitter to extract a page range into its own file.
PDF to Image
Online PDF to image converter when a page is needed as a picture.
Organize PDF
Online PDF organizer for pages that need moving or dropping.
OCR PDF
Online OCR to PDF for a scan that needs searchable text.
PDF Locker
Online PDF locker when the compressed file needs a password.
Image Compressor
Online image compressor to shrink pictures before they go into a PDF.
All PDF Tools
Every document utility in one index.
Authorship

Who Maintains This Online PDF Compressor

OnlinePCApps PDF Group

PDF internals since 2013

Compiled and checked by Last reviewed September 2026
13
Years at it
110
Utilities live
2
ISO standards used
0
Copies kept here

Document and file format tooling has been this company's work since 2013, starting with desktop software that read container formats directly rather than through a vendor library. The online PDF compressor keeps that discipline to one choice: a profile named for the quality it keeps, applied to the entire document in one pass.

Standards referenced

ISO 32000 · PDF syntax JPEG · Image encoding Font subsetting FileReader API Image resampling

What it is tested against

Scans at 200, 300 and 600 dpi from flatbed hardware, sheet-fed units and phone camera capture Text-only documents, to confirm the tool reports a small reduction rather than inventing one Documents whose images are already below the target resolution Files already compressed once, to measure what a second pass actually returns Exports from PowerPoint and Excel that mix vector charts with photographs on one page Output opened in Acrobat, Preview and Chrome to confirm rendering is unchanged
About the group Technical notes Report a bad result
Seen the online PDF compressor handle a document badly? Report it and the case gets looked at.

Compress PDF Files Online Free

No install, no account, no paid tier. One profile in the online PDF compressor, one click on Compress PDF and the smaller file downloads.

Compress a PDF Free, no account The Desktop Build For directory-level runs
Compress PDF · Free