Percentage sliders hide the contract. A banner that must be 728×90 is not “make it smaller.” Developers, performance marketers, and anyone filling a government pixel field belong here. Canvas reports the source size so you can do the arithmetic: if you lock aspect and change width, height follows.
Off-by-one outputs from some cloud tools break CSS that expects 1200 exactly. Local Canvas matches the integers you typed. Upscaling past the source cannot invent samples — 10,000 px is a ceiling, not a detail machine.
Before upload to a portal that also has a KB cap: lock the pixel box here, then encode. Doing bytes first on a 6000px still is backwards.
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Integer arithmetic without a hidden crop
Spec sheets use absolute pixels
App Store screenshot lists, IAB standard ads, LinkedIn OG-ish cards, and many LMS avatars print width×height. Type those numbers. If the source aspect differs, crop first (Crop Image) or accept letterboxing in your layout — stretching a face to force 16:9 is usually wrong.
Aspect lock is a sharpness strategy
Geometric distortion reads as “soft” even when the sampler is good. Keep lock on for photographs. Disable it for a forced UI slot (and check the preview). Circles in logos should not become ovals.
Pre-upload control
Servers that auto-crop to a square will ignore your composition. Export the box they actually display. You keep quality and privacy; they get fewer excuses to slice the subject.
How it works
- 1
Read the source width and height
Canvas shows the baseline. If you are about to enlarge a lot, stop and find a larger master.
- 2
Enter the integers from the spec
Lock aspect for proportional scale. Unlock for a forced rectangle. Preview.
- 3
Download and confirm in file properties if a portal is pedantic
Some forms reject 1199×627. You typed 1200×627 — local draw should match.
Use cases
Store listing screenshots
Apple and Google pixel lists, exactly.
IAB and paid slots
728×90, 300×250, 160×600 — rejection emails are aspect errors.
Sprite and UI frames
Normalize frame size for engines and design systems.
Form avatars
400×400 or 600×600 before a KB encode pass.
Problems we solve
“50% smaller” when the spec says 628×1200
Percentages are relative. Specs are absolute. Use integers.
Silent stretch
Unlocked aspect on a portrait still in a landscape box. Lock it.
Cloud rounding
Off-by-one breaks CSS. Canvas uses your integers.
Trust & technology
Integer output
What you type is what is drawn.
Private local edit
Custom boxes never leave the browser on this path.
Live preview
See the box before you download.