A browser will happily paint a 4000-pixel photograph inside a 600-pixel column, and it downloads every one of those wasted pixels first. Shrinking the picture before it ever reaches a page is the fix, and the Image Resizer does that job in this tab: you give it a width, a height, or a percentage, and it redraws the image at that size and hands the file back. No queue, no watermark.
Two details separate it from dragging a corner in a photo app. The aspect-ratio lock derives the second dimension from the one you typed, so a 1600 × 900 source pushed down to a width of 800 lands on 800 × 450 with no arithmetic from you. The smooth-downscale pass then halves the image repeatedly on its way to the target instead of leaping there in a single draw, and that is the whole difference between legible 10-pixel type and grey mush, because a one-shot reduction below 50% skips source pixels rather than averaging them.
Your file is never uploaded. It is decoded from a local object URL, redrawn on a canvas element, and returned as a download, which means a client photograph or a scanned document stays on the machine you opened it on. Output keeps the source format by default, or you can force JPEG, PNG, or WebP and set the encoder quality yourself.
Getting Your Image to a New Width
- Drag a file onto the drop panel, or press Load Sample Image to paint the built-in test card, a 1600 × 900 grid captioned
1600 × 900 above resizer test card, with a 100 px ruled grid and eight flat colour bars. - With Pixels selected, type into Width. While the chain button between the two fields is lit, Height recalculates from the source ratio on every keystroke; the six Common widths chips fill in 1920, 1280, 1080, 800, 400 and 150 for you.
- Choose Percent instead when the reduction is relative rather than absolute, then tap one of the 25% to 200% chips or type any value you like.
- Set Output Format and drag Quality. There is no render button: every change re-encodes automatically about a quarter of a second after you stop typing, and a Rendering badge sits above the preview while that happens.
- Check the three stat cards for the new dimensions, the encoded file size and the change against the original, then press the wide terracotta Download button, which names the file after your source plus its new dimensions.
- Before you leave, copy the HTML with explicit dimensions block. It is easy to scroll past, and pasting that
<img> tag with its width and height attributes already filled in is what stops the page jumping around as images load.
How Big the Output File Gets
- A percentage applies to each side, not to the area. Halving 1600 × 900 to 800 × 450 removes three quarters of the pixels, so the encoded file normally drops by much more than half.
- Re-encoding can produce something bigger than what you started with, which is common when a flat PNG screenshot is written back out as a high-quality JPEG. The third stat card turns red and reads Larger in that case rather than pretending the change was zero.
- Each side is capped at 10000 px. Type past it and the tool refuses with
Width must be a whole number between 1 and 10000 pixels., and the preview clears until the number is valid again. - Loading anything heavier than 25 MB raises an amber notice first, because mobile Safari tends to hand back an empty canvas around that point instead of an error.
- Decimals are rejected outright in pixel mode, while percent mode rounds: 33% of a 1600 px width resolves to 528 px.
What It Accepts and What It Writes Back
- Reads JPEG, PNG, WebP, GIF and BMP. Hand it anything else and it answers
That file is not an image. Pick a JPEG, PNG, WebP, GIF, or BMP. - Canvas can only write JPEG, PNG and WebP, so a GIF or BMP left on Keep source format comes back as PNG. An animated GIF contributes its first frame only.
- Exporting a PNG, WebP or GIF as JPEG reveals a Background behind transparency colour well, defaulting to white, because JPEG carries no alpha channel and transparent pixels would otherwise read as black.
- The Quality slider is inert on PNG output and says so on screen; it drives the encoder only for JPEG and WebP.
- Unlock the chain and the tool still obeys you, but it posts the old and new ratios side by side and warns that the result will be stretched.