How to reduce image file size without losing visible quality

To make an image much smaller without a visible difference, reduce its pixel dimensions first, then save it as JPG or WebP at quality 75–80. Dimensions are the lever that matters: quality settings alone rarely give you more than a two-fold saving, while halving the width and the height removes three quarters of the pixels.

The quickest route here: drop your files into Compress image, set the quality to 75–80, tick the maximum-width option and enter 1920, then download. If a form demands an exact figure such as "under 50 KB", use Resize image in KB instead, which searches for the highest quality that still fits.

Lever 1: dimensions (the biggest win)

File size grows with the number of pixels. A 12-megapixel phone photo is 4000 × 3000, or 12 million pixels. Resized to 1920 × 1440 it holds 2.76 million — about a quarter as many — and it still covers a Full HD screen edge to edge.

The arithmetic is worth doing once. An uncompressed 24-bit image needs three bytes per pixel, so those 12 million pixels are 36 MB of raw data before any compression; the same photo at 1920 × 1440 is 8.3 MB of raw data. JPEG compression then works on a quarter of the material, and the output shrinks roughly in proportion.

Use	Sensible maximum width	Typical result from a phone photo
Email attachment	1600–2000 px	300–600 KB
Blog or website content image	1200–1600 px	150–400 KB
Full-width website hero	1920–2560 px	400–900 KB
Instagram post	1080 px	150–350 KB
LinkedIn or Facebook link preview	1200 × 630 px	100–250 KB
Thumbnail or avatar	400–600 px	20–80 KB

The figures in the right-hand column are what a typical outdoor photo lands at around quality 75–80. A picture of a plain wall compresses far smaller; foliage, crowds and noise compress worse, because JPEG spends bytes on fine detail.

Use Resize image when you want a specific width, or the maximum-size option inside Compress image when you just want a ceiling.

Lever 2: quality

JPEG and WebP are lossy: they discard detail the eye barely notices, and the quality number decides how much.

• 85–92 — visually identical to the original at normal viewing distance. Use it for portfolios, print masters and photos you will edit again.
• 70–80 — the working range for the web and email. On photographs the difference is very hard to see, and the file is often half the size of the same image at 90.
• Below 60 — blocks appear in skies and gradients, and halos appear around text and hard edges. This is what makes a scanned ID card unreadable.

Quality settings are not a scale you can compare across programs: quality 80 in one encoder is not exactly quality 80 in another. Treat the number as a dial you check by eye, not as a measurement.

Lever 3: format

Format	Compression	Transparency	Best for	Watch out for
JPG	Lossy	No	Photographs, anything that must open everywhere	Poor on text and sharp edges
PNG	Lossless	Yes	Screenshots, logos, diagrams	2–5× bigger than JPG for photos
WebP	Lossy or lossless	Yes	Photos and graphics on the web	Some older desktop software and upload forms refuse it
SVG	Vector	Yes	Logos and icons	Not usable for photographs

WebP is typically 25–35% smaller than JPG at comparable visual quality, and it is displayed by every current browser. For screenshots and illustrations, converting PNG to WebP often removes 60–80% of the file size. Convert with JPG to WebP or PNG to WebP; when a site or form rejects WebP, go back the other way with Image converter.

What re-encoding actually does to your file

• It is a new file, not an edit. The pixels are decoded and encoded again, so a saved-then-resaved JPEG has been through the lossy step twice. Each pass degrades what the previous one already degraded — this is generation loss, and it is why you should always start from the original rather than from a file you compressed yesterday.
• Metadata is dropped. EXIF, including the GPS coordinates most phones record, does not survive a re-encode. That is usually welcome; see how to remove location from photos if it is the point of the exercise.
• Transparency has to go somewhere. Saving a transparent PNG as JPG puts the transparent areas on a solid background (white in our tools). Keep PNG or WebP if the transparency matters.
• Nothing can be restored. Detail removed by compression is gone. Raising the quality of an already-compressed file only produces a bigger file with the same defects.

Putting it together

A 6 MB phone photo, resized to 1920 px and saved at quality 75, usually lands between 300 and 500 KB — around ten times smaller, with no visible difference on a screen. If you need it under a fixed limit instead of "as small as sensible", do the resize first and the size target last, because resizing after hitting the target changes the size again.

What the built-in apps can and cannot do

• Windows Photos crops, rotates and resizes, and its resize dialog offers a quality slider and pixel dimensions. It does not let you aim at a file size in KB.
• macOS Preview resizes with Tools > Adjust Size and re-encodes with File > Export, where the quality slider shows the resulting size as you drag it. It has no batch mode for a folder of photos.
• iPhone Photos can crop and rotate but cannot resize to pixel dimensions. Mail offers a size choice (Small, Medium, Large, Actual Size) when you attach a photo, which is a resize in disguise.
• Android Google Photos edits and crops; resizing and size targets depend on the manufacturer's gallery app, so they are not something you can count on across devices.

Questions people ask

Does resizing lose quality? Making an image smaller keeps it sharp — you are throwing away pixels you were not displaying anyway. Enlarging is what softens an image, because the extra pixels are interpolated from neighbours.

Why is my PNG screenshot 4 MB? PNG stores every pixel exactly, and a full-resolution screenshot of a photo-heavy page is a lot of pixels. Convert it to WebP, or to JPG if the screenshot contains no text you need crisp.

Can I compress a photo twice to get it smaller? You can, but you should not. Go back to the original and compress once, harder. Two passes at quality 80 look worse than one pass at 70 and are rarely smaller.

Is 1 KB 1000 or 1024 bytes? Both conventions exist. Windows counts 1 KB as 1024 bytes, macOS displays 1 MB as 1,000,000 bytes, and most upload forms use 1024. Our KB tool uses 1024, which is the safer assumption when a limit is tight.

Does compressing remove the photo's date and location? Yes, re-encoding drops EXIF. If that is your goal, verify it with Image metadata viewer rather than assuming.

Next steps

• Aim at an exact limit with Resize image in KB.
• Decide between formats with our guide JPG vs PNG vs WebP.
• If the file being refused is a PDF or a scan, read your file is too big for the upload form.