Free · browser-based · no uploads
Reduce the size of images and PDFs — right in your browser
Reduce image size to a hard KB target, reduce the size of PDF files, and run the full PDF suite — compress, merge, split, protect, unlock, convert and sign. Nothing uploads to a server: your browser does the processing, and every result is measured from the real output, not promised.
Target size
Resize pixels (optional)
Aspect ratio is always preserved. Leave blank to keep the original pixels.
Drop images here
JPG · PNG · WebP — up to 24 files per batch
Nothing uploads — works offline once loaded
Measured before → after on every file
Batch of 24, one-click ZIP
How it works
01
Drop your files in
One image or twenty — the queue takes up to 24 files and processes them on your device.
02
Pick the size that matters
A hard cap for a portal, a lean email size, or no target at all — plus an optional pixel limiter.
03
Get measured results
Every card shows before → after in real bytes, the levers used, and a straight state: target met, best effort or no gain.
Image tools
- Compress to 20 KB
- Compress to 50 KB
- Compress to 100 KB
- Compress to 200 KB
- Compress to 1 MB
- Reduce size for email
- Reduce size for documents
- All image tools
Target pages preselect the cap for you: exam forms, signature scans, email photos. Every tool shares the same honest engine.
PDF tools
Structural tools are lossless; compression rasterises and says so. Passwords stay in your browser.
Guides
Real limits, real formulas, no fairy tales
Exam-form caps, passport dimensions, phone workflows and what “compress a PDF” does to a scan — honest numbers, each guide linking to the right tool.
Read the guidesQuestions, answered plainly
What does “reduce size” mean?
Making a file take up less disk space by re-encoding it. Bytes are traded against detail, and the trade is shown on the result card rather than hidden.
How do I decrease the size of a file?
Use the image compressor for photos and the PDF compressor for documents: drop the file in, pick a target, read the measured result. Nothing uploads.
How do I reduce a file to 5 MB, 20 MB, or another target size?
Type it into the custom target field. Images take KB or MB; PDFs take KB, so 5 MB is 5000 KB. If the cap is out of reach, the card explains why.
How can I reduce file size without losing quality?
Bytes always cost something, but the engine re-encodes at the highest quality that still fits, so a small reduction is visually identical. Compressing a PDF rasterises its pages, so text stops being selectable — split the document instead when that matters.
Why is my file still large after compression?
Usually one of three causes: a digital-text PDF with little waste to squeeze, an already-optimised file (“no gain”), or an image whose detail fights your cap.
Which files can I reduce here?
JPG, PNG and WebP images — up to 24 per batch — and PDF documents. There is no video or archive support, and files of hundreds of MB are impractical for a browser.
Are my files uploaded to a server?
No. Your browser does the work, so no copy of your file ever leaves the device. Once the page has loaded, the tools keep working offline.
What do “Target met”, “Best effort” and “No gain” mean?
Target met: the measured output is at or under your cap. Best effort: the cap was not honestly reachable — smallest workable size plus the reason. No gain: already optimised. An oversized result is never labelled success.
Is ReduceSize Online really free?
Yes — no account, no watermark, no daily caps. The tools run on your own device, which is why they cost nothing to give away.
What Reduce Size Online does
Reduce Size Online is a free suite of browser-based tools for one everyday job: making a file fit a limit. Upload caps read like “photo below 100 KB” or “PDF under 2 MB”, and a machine rejects the file long before a human looks. The tools reduce the size of your images and PDFs to the requested number, and tell you what it cost.
Everything runs on your device: nothing uploads, and “done” means the bytes were counted from the actual output file.
How to reduce image size to an exact KB or MB limit
First pick the target your form or task demands — each page preselects it for you: 20 KB, 50 KB, 100 KB, 200 KB or 1 MB. Then drop files in — a JPG, PNG or WebP, or up to 24 at once — and read the result card: measured before → after in real bytes, plus the honest state of the attempt.
Two details matter for forms. If the portal names pixel dimensions, the dimension limiter resizes while preserving aspect ratio. To reduce the size of a JPG while keeping every pixel — say, reduce JPG size to 100 KB — the compressor runs on quality alone and steps down dimensions only when the target demands it.
How to reduce the size of a PDF
It starts with knowing which of two documents you hold. Scanned PDFs — pages that are really photographs — re-encode beautifully, and a 5 MB scan regularly lands under 1 MB with no readable loss. Digital-text PDFs have nothing wasteful to give up, so the PDF compressor checks for a text layer and reports the situation instead of silently rasterising away selectable text.
The rest of the suite is lossless by design: merge, split by page ranges, add an AES-256 password, remove a password you know, export pages via PDF to JPG, or stamp a drawn signature with the signing tool.
How the compression works
Reducing an image’s bytes is a measured search: re-encode at successive quality levels, keep the best attempt under your cap, and reach for a resolution step or an explicit format change only when quality alone cannot close the gap. Every lever used is named on the card, and if no honest attempt reaches the target you get best effort — the smallest workable file plus the reason.
Formats, features and honest limits
Images accept JPG, PNG and WebP, batches run up to 24 files, and ZIP downloads keep a big job to one attachment. Transparency is handled on your terms: a transparent PNG is never flattened silently — you choose an alpha-preserving WebP or an explicitly labelled flatten step. On the PDF side, target-size compression, lossless page operations, AES-256 encryption and drawn signatures all run locally. The limits are stated because they are real: an already-optimised file gets a no gain state, not a pointless second pass.
Where reducing size matters most
Application portals enforce hard caps on photos, signatures and scans — the documents and forms use-case covers common exam-form bands. Email and messaging care about attachment weight —reduce image size for email runs from inline images to a batched ZIP. The guides add the numbers behind passport scans and phone workflows.