Most online image tools upload your files to a server. You do not know what happens to them after processing. Are they stored? Analyzed? Shared with third parties?
ToolKnife's image tools process everything in your browser using the Canvas API. Your images never leave your device.
How client-side image processing works
When you drop an image into ToolKnife's image resizer, here is what happens:
- Your browser reads the file into memory (using the File API)
- The image is drawn onto an HTML Canvas element
- The Canvas API applies the transformation (resize, crop, rotate, filter)
- The result is exported as a new file (PNG, JPG, or WebP)
- You download the processed image
At no point does the image cross the network. Open your browser's Network tab while processing an image. You will see zero upload requests.
Available image tools
Resize
The Image Resizer scales images to exact dimensions. Lock aspect ratio, set max width/height, or enter custom dimensions.
Common use: resize product photos, social media images, blog thumbnails.
Compress
The Image Compressor reduces file size with a quality slider. See the before/after size comparison in real time.
A 4MB product photo compressed to 200KB with no visible quality loss. That is the difference between a page that loads in 1 second and 5 seconds.
Crop
The Image Cropper lets you crop with preset aspect ratios (1:1, 16:9, 4:3, 3:2) or free-form. Rule-of-thirds grid overlay for composition.
Rotate and flip
The Image Rotator handles 90/180/270 degree rotation and horizontal/vertical flipping. Also supports free rotation with a slider for any angle.
Convert format
The Image Format Converter converts between JPG, PNG, and WebP. WebP is typically 25-35% smaller than JPG at equivalent quality.
Remove background
The Background Remover uses color-keying to remove solid backgrounds. Click the background color, adjust tolerance and feather, and download the transparent PNG.
Best for: product photos on white/solid backgrounds.
Watermark
The Image Watermark adds text watermarks with 6 position options, adjustable opacity, rotation, and color. Useful for protecting portfolio images.
Metadata stripper
The Metadata Stripper removes EXIF data (camera model, GPS coordinates, date taken) from photos before sharing. Your phone photos contain your exact location. Strip it before posting.
Filters
The Image Filters tool applies 10 presets (Vintage, Noir, Dramatic, Warm, Cool, etc.) plus 7 manual sliders (brightness, contrast, saturation, blur, hue rotate, sepia, grayscale). Generates the corresponding CSS filter string.
Privacy comparison
| Tool | Uploads to server? | Data retention? |
|---|---|---|
| ToolKnife | No | No (client-side) |
| TinyPNG | Yes | Deleted after processing |
| Remove.bg | Yes | Deleted after 1 hour |
| Canva | Yes | Stored in your account |
| Photopea | No (client-side) | No |
Client-side processing means:
- No data leaves your device. Verifiable via Network tab.
- Works offline. Once the page loads, processing works without internet.
- No file size limits. Server tools often cap at 5-10MB. Client-side handles whatever your browser can fit in memory.
- GDPR/HIPAA compliant by design. If you do not collect the data, there is nothing to protect.
When you need a server
Client-side processing has limits:
- AI-powered background removal (like Remove.bg) uses ML models too large for the browser
- Batch processing of hundreds of images is faster on a server
- Format support for raw camera files (CR2, NEF) requires specialized decoders
For these, a server is necessary. For everything else (resize, compress, crop, convert, watermark, metadata strip, filters), client-side works and is faster.
For developers
All image tools are available through the API for server-side processing:
# The API runs the same logic server-side when you need programmatic access
curl -X POST https://toolknife.com/api/v1/tools/image-resizer_resize \
-H "Content-Type: application/json" \
-d '{"width": 800, "height": 600, "maintainAspectRatio": true}'
Or embed them on your site:
<iframe
src="https://toolknife.com/embed/image-compressor"
width="100%"
height="500"
style="border: none;"
title="Image Compressor"
></iframe>