⚡ 10-second version
Most resizers give you a width box. tooladda.online/image-resizer.html also lets you choose how the pixels are rebuilt — which is the difference between a crisp downscale and a smeared one.
❗ Important
Resizing happens on your machine. Nothing is uploaded, so batch-resizing 60 photos costs you no bandwidth and leaks no EXIF.
🔬 The algorithm actually matters — here's when
Resizing means inventing or discarding pixels. Four common ways to decide what each output pixel should be:
| Algorithm | How it decides | Use it for | Avoid it for |
|---|---|---|---|
| Nearest neighbour | Copies the single closest pixel | 🎮 Pixel art, sprites, QR codes — keeps hard edges perfectly crisp | Photographs — you get jagged, blocky stairsteps |
| Bilinear | Averages the 4 surrounding pixels | Quick previews, mild changes | Large downscales — noticeably soft |
| Bicubic | Weighted 16-pixel cubic fit | 📷 General photo work; a safe default | Very large downscales (still softer than Lanczos) |
| Lanczos | Windowed sinc over a wider neighbourhood | 🏆 Big downscales and detailed photos — the sharpest realistic result | Pixel art (it will blur your hard edges) |
The counter-intuitive bit: the "best" algorithm depends on the content, not the quality you want. Scale a QR code or a game sprite with Lanczos and you'll destroy it — the crisp block boundaries that make it readable get blended into grey mush. Nearest neighbour, normally the "worst" option, is the correct one there.
Upscaling can't add detail
Enlarging a 500 px image to 2000 px does not recover information that was never recorded. Every algorithm is guessing. Lanczos guesses more pleasantly than bilinear, but if you need a big image, start from a big image.
Downscale, then sharpen
Any good downscale slightly softens the result — that's the averaging doing its job. A small sharpening pass afterwards is standard practice and makes a resized photo look intentional rather than blurry.
🧭 How it works
✨ What's inside
| ### 🎛️ Algorithm choice Four resamplers, selectable per job — not one hidden default you can't inspect. This is the feature almost no free resizer exposes. | ### 📱 Social media presets Correct dimensions for profile pictures, posts, stories, covers and thumbnails, so you stop looking them up every time. |
| ### 📦 Batch resize Whole folders in one pass, out as a ZIP, using web workers so the tab stays usable while it runs. | ### 🖨️ DPI control Set the DPI tag for print workflows — the thing that decides whether your 3000 px image prints at 10 inches or 30. |
🛠️ Real jobs
| Situation | Setting to use |
|---|---|
| 🌐 Website images | Resize to the actual display width; Lanczos; then compress |
| 📱 Profile picture | Social preset; square crop; Bicubic |
| 🎮 Pixel art / sprite sheet | Nearest neighbour, integer multiples (2×, 3×, 4×) |
| 🖨️ Print at a known size | Set pixel dimensions for 300 DPI at your target inches |
| 📤 Upload form with a px cap | Exact pixel dimensions, then compress to the KB limit |
| 📚 Whole photo archive | Batch mode, percentage scaling, ZIP out |
📖 Five steps
1. Open → tooladda.online/image-resizer.html
2. Drop → one image or a whole batch
3. Size → pixels, percentage, or a social preset
4. Method → Lanczos (photos) · Nearest (pixel art / QR)
5. Export → download, or ZIP for a batch
▶ Resize now — tooladda.online/image-resizer.html
💡 Tip
Resize before you compress, never after. Fewer pixels is a bigger and cleaner saving than a lower quality setting — and compressing then resizing means you paid the quality cost twice.
❓ FAQ
Is it free? Watermark or batch limit?
Free, no watermark, no signup, and the batch limit is your device's memory.
Which algorithm should I just pick?
Lanczos for photographs, especially when shrinking a lot. Nearest neighbour for pixel art, QR codes and anything with deliberately hard edges.
Can I make a small image large and sharp?
No. Upscaling interpolates; it cannot recover detail that was never captured. Start from a larger original.
Why does my downscaled photo look slightly soft?
That's normal for correct resampling. Apply a light sharpen afterwards — standard practice in every professional workflow.
Does changing DPI change the pixels?
No. DPI is a tag telling a printer how densely to lay those pixels down. Same pixels, different physical size on paper.
Are my images uploaded?
No — everything is processed locally in your browser.
🔬 Under the hood
- Vanilla JavaScript with a real Lanczos implementation, not just the browser's default canvas scaling.
- Batch work offloaded to web workers so large sets don't freeze the tab.
- Aspect ratio locking, percentage and absolute modes, DPI metadata writing.
- Offline-capable once loaded.
Originally published on ToolAdda, where Image Resizer runs free in your browser — nothing is uploaded, nothing leaves your device.
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