How to compress images on Windows

Short answer: re-save the photo as JPEG at a lower quality — around 75–85 — or hit an exact size limit. Paint sort of does the first, one file at a time; online compressors upload your photos to someone else's server; a free offline app like Image Compressor does both in a batch — slide JPEG quality from 10 to 95, or type “2 MB” and it binary-searches the quality until the file fits.

Why photos are so big in the first place

Three separate things make image files huge, and it helps to know which one you are fighting:

Resolution. A modern phone or a 24 MP camera produces 6000×4000 pixels. Every pixel costs bytes, and pixels you cannot even see in a chat window are still stored in the file.
JPEG quality. Cameras save at quality 90–95 to be safe. Dropping to 75–85 typically halves the file with no visible difference; below roughly 60 the artefacts start to show in hair, foliage, skies and skin.
Format. Screenshots and graphics are usually PNG — lossless, perfect for text and flat colours, and terrible for anything photographic. A 1920×1080 screenshot as PNG can be 3–5 MB; the same picture as JPEG at quality 85 is a few hundred kilobytes.
And the classic: a photo that was already compressed once, opened, slightly edited and saved again at quality 95 — which can be bigger than the original.

Method 1: online image compressors

Search for “compress image” and you get a wall of websites: upload, wait, download. They work, and for one unimportant picture that is fine. The catches, in order of how much they hurt:

Your file is uploaded. The photo spends time on a server you do not control and leaves your PC — a problem for documents, family pictures and anything under NDA.
Limits. Free tiers cap upload size (often 5–20 MB), the number of files per day, and sometimes even the output resolution.
Watermarks and fixed quality. Some free services stamp a logo on the result or re-encode at a quality you cannot choose.
Availability. The site is down, the queue is long, or the page is covered in fake “Download” buttons that are actually ads.

Method 2: Paint and the Photos app

The built-in route is honest but limited.

Paint — open the image, File → Save as → JPEG. Paint re-encodes the picture, and on some versions the save dialog offers a compression level; Windows 11's Paint gives you “Save as JPEG” with no quality control at all. It is one file at a time, about twenty seconds each, and there is no way to say “make it under 2 MB”. And always Save as — plain Save overwrites your original.

Photos app — the … menu → Resize. This changes the pixel dimensions, which does help, but it does not increase JPEG compression: a 12 MP photo resized to 2 MP keeps its quality-95 encoding, so the file shrinks far less than it could. Again: one image at a time, no target size, no report of what actually happened.

Method 3: Image Compressor — two modes, no upload

Download free — ImageCompressor-Setup.exe

Add the photos — JPEG, PNG, WebP, BMP, GIF or TIFF. The list is remembered between runs, so a whole folder is a single drag.
Pick a mode. Quality slides the JPEG quality from 10 to 95 — 75–85 is the sweet spot for photos. Target size takes a number in KB or MB, and the app binary-searches the JPEG quality until the file fits, reporting the quality it settled on. Set a max side in pixels and oversized photos are downscaled before saving too.
Press “Compress N images.” Every row shows the result — 4.8 MB → 620 KB · saved 87% · quality 74 — and the header totals the whole batch.

Outputs are new .jpg files next to the originals (or in a folder you choose), so nothing is ever overwritten and an experiment costs nothing. If even the lowest quality cannot reach your target, the row says “target not reached” instead of quietly overshooting. Transparency is flattened onto white, not black. And the whole thing runs on your PC — nothing is uploaded, Wi-Fi off changes nothing.

How much can you safely compress?

Photos: JPEG quality 75–85. At 85 the difference from the original is essentially invisible on screen; at 75 only a careful side-by-side reveals it, and the file is often half the size. Below 60, expect visible blockiness — especially in smooth skies and skin.
For messengers and quick sharing: 70 or less, plus a smaller max side. Chats re-compress anyway, so delivering a 1600 px, quality-70 file avoids the platform doing it worse.
Be careful with screenshots, logos, diagrams and smooth gradients. Text edges and flat colour areas show JPEG artefacts quickly: use quality 85–90 for anything with text, or shrink the pixel dimensions instead — halving the width cuts the file to about a quarter with no quality loss at all.

FAQ

Does compressing photos reduce quality?

Every JPEG save is lossy, but the trade is generous: at quality 75–85 the difference is invisible in normal viewing, while the file is often 40–70% smaller. The real danger is repeated re-saving — which is why Image Compressor never touches your originals, so a second attempt always starts from the untouched source.

Can I compress an image to an exact size, like “under 2 MB”?

That is what target-size mode is for: type 2 MB (or 500 KB), and the app binary-searches the JPEG quality until the file fits the limit — the same “bisection” approach a serious image pipeline uses, done in milliseconds. If the limit is impossible for that image, it tells you “target not reached” rather than pretending.

Do I need to install anything?

No — but you lose control without it. Paint and the Photos app ship with Windows and handle single images only; browser compressors need an upload. Image Compressor is a small offline installer (Windows 10/11 x64) with no accounts, no ads, no telemetry and no size limits.

More: how to resize images on Windows and how to convert WebP to JPG on Windows.