Is my image uploaded to a server?

No. The image is decoded and redrawn on an HTML Canvas entirely in your browser. It never leaves your device, which makes the tool safe for private photos and unreleased assets.

Which output format should I choose?

Use JPEG for photographs to get small files with a quality slider, PNG when you need lossless output or transparency, and WebP for the best compression at a given quality where browser support allows.

Will resizing keep the aspect ratio?

When aspect-ratio lock is on, you set the width and the height is computed automatically so the image is not stretched. Turn the lock off to set both dimensions independently.

Why does upscaling look blurry?

Enlarging an image cannot add detail that was not captured, so the Canvas interpolates between existing pixels and the result softens. For best quality, resize down from a larger original rather than up from a small one.

What does the quality slider do?

For JPEG and WebP it controls the lossy compression level from 0.1 to 1. Lower values shrink the file but introduce artefacts; 0.8 to 0.9 is a good balance. PNG is lossless, so the slider does not apply.

What is the Image Resizer (Local)?

Free local image resizer. Resize PNG, JPEG, or WebP images to exact pixel dimensions or a percentage with aspect-ratio lock and a quality slider, all on a Canvas in your browser. Nothing is uploaded to any server. It runs free in your browser on Gera Tools, with nothing uploaded.

Image Resizer (Local)

Name: Image Resizer (Local)
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Get one useful tool a week

Like this tool? Enter your email and we'll send you one genuinely useful Gera tool a week — plus a link to come back to this one. No spam, one-click unsubscribe any time.

Resizing an image changes its pixel dimensions — useful for fitting an upload size limit, generating thumbnails, preparing photos for a CMS, or trimming a large camera file down to a web-friendly size. This tool does the resize on an HTML Canvas right in your browser, so your image is never sent anywhere.

How it works

The tool loads your file into an Image object to read its natural width and height. When you resize:

A Canvas is created at the target dimensions.
drawImage redraws the source into that Canvas with imageSmoothingEnabled = true and imageSmoothingQuality = "high", which applies bilinear interpolation for clean scaling.
The Canvas is exported with toBlob in your chosen format and quality setting.

Format and quality guide

Format	Quality slider	When to use
JPEG	Yes (0.1–1.0)	Photographs; 0.80–0.90 is the sweet spot
PNG	No (lossless)	Transparency needed; line art; logos
WebP	Yes (0.1–1.0)	Modern web pages; best size at given quality

A quality setting of 0.85 in JPEG or WebP typically produces results indistinguishable from 0.95 at significantly smaller file size.

Worked examples

Blog post image: Original is a 4032×3024 phone photo. Target: 1200px wide for a blog column. With aspect ratio locked, enter 1200 in the width field; the height computes automatically to 900. Export as WebP at 0.85. The result is a fraction of the original file size at full visual quality.

Avatar or thumbnail: Profile images often need to fit a 200×200 or 400×400 square. If the source is a portrait photo with a 3:4 ratio, you will need to either unlock the aspect ratio (which squashes the image) or crop to square first. For the best result, crop the photo square before resizing to the target.

Platform upload limits: Many CMS and social platforms reject images over a certain pixel dimension or file size. Set the max dimension to the platform’s limit (for example 2048 or 1920), choose JPEG at 0.85, and the result reliably fits under most size caps.

Upscaling limitation

Canvas interpolation fills in missing pixels by blending neighbours. The result looks soft because no new detail is being invented. For best upscaling quality, start from the largest original you have and scale down. AI-powered upscaling tools produce sharper results for enlargement than Canvas-based resizing can.

Common platform dimension requirements

Platform	Recommended max dimension	Notes
Twitter/X header	1500 × 500 px	Use exact dimensions
Instagram post	1080 × 1080 px (square)	Also 1080×1350 portrait
LinkedIn banner	1584 × 396 px
Website hero	1920 px wide	Compress after resizing
Email header	600 px wide	Wider causes mobile layout breaks
Etsy listing	2000 px shortest side	Min for zoom feature

The dimensions above are guidelines — always check each platform’s current documentation, as requirements change. This tool handles the resize; use the Image Compressor tool afterward if you also need to hit a specific file size.

Nothing is uploaded — all processing stays in your browser.