Image Compressor for JPG, PNG & WebP — Core Format
TARGET-SIZE & QUALITY IMAGE COMPRESSOR
Online Image Compressor
Compress JPG, PNG, and WebP images directly in your browser. Choose between manual quality adjustment or compress to an exact target file size (e.g. 50 KB, 100 KB, 200 KB) with zero server uploads.
Select images to compress
Drag and drop JPEG, PNG, or WebP files here, or choose from device.
Up to 50 files, 40 MB each; 200 MB per batch.
Maximum 40 megapixels and 12,000 pixels per side.
All compression runs locally in your browser. Your images are never uploaded to any server.
Ready to compress. Select your images to begin.
How to compress images to a target size or quality
- Select your images: Drag and drop up to 50 JPG, PNG, or WebP files into the workspace, or click “Select Images”.
- Choose your compression mode:
- Target File Size Mode: Enter an exact byte target (e.g. 100 KB, 200 KB) or choose a quick preset. The algorithm iteratively optimizes compression to meet your target without dropping below your minimum quality threshold.
- Adjust Quality Mode: Manually tune the quality slider (70%–80% recommended) to compress while maintaining fixed original dimensions.
- Control dimensions: By default, original dimensions are strictly preserved. To meet tight size targets (such as under 50 KB or 100 KB for online forms), enable “Reduce dimensions if quality alone cannot meet target”.
- Compare and inspect: Use the “Compare” button to inspect side-by-side pixel clarity before and after compression on a transparency checkerboard.
- Download your assets: Save individual compressed images directly or pack the entire collection into a single ZIP archive.
Intelligent compression across formats
Different image formats encode visual data in fundamentally different ways. CoreFormat’s Image Compressor adapts its processing engine based on file type:
| Format | Compression Method | Transparency | Target Size Support |
|---|---|---|---|
| JPEG / JPG | Discrete Cosine Transform (DCT) lossy compression with iterative quality probing. | Not supported (composited on white if converted). | Yes, iterative bounded search. |
| WebP | VP8/VP8L prediction-based encoding with macroblock quantization. | Fully preserved with 8-bit alpha channel. | Yes, iterative bounded search. |
| PNG | Deflate compression with palette quantization and color reduction. | Fully preserved. | Supported via adaptive palette reduction or WebP conversion. |
How does target-size compression work?
Image encoders are non-linear; the exact byte size of a compressed image cannot be calculated in advance without encoding. Our client-side engine executes a bounded binary search across compression parameters:
- Bounded Iterations: The tool performs up to 6 rapid encoding passes in memory, checking actual generated byte counts after each iteration.
- Best Valid Candidate: The engine tracks the best candidate that satisfies your target size without dipping below your specified minimum quality threshold.
- Transparent Reporting: If an image cannot meet your target without degrading below acceptable quality, the tool honestly marks the result as “Target Not Met” and shows the closest achievable size. We never falsely label an oversized image as successful.
Frequently Asked Questions
Does target size compression reduce image pixel dimensions?
Only if you explicitly enable the “Reduce dimensions if quality alone cannot meet target” option. By default, dimensions are strictly preserved. If an image cannot reach the target size through quality compression alone, it will notify you rather than silently shrinking your image.
What byte standard is used for KB and MB?
We use standard binary units matching operating system file sizes: 1 KB = 1,024 bytes and 1 MB = 1,048,576 bytes. For example, a target of 100 KB equals exactly 102,400 bytes.
How does PNG compression work compared to JPG?
Standard PNG format uses lossless Deflate compression, meaning it does not have a continuous lossy quality slider. In our tool, adjusting PNG quality or setting a target size applies palette color quantization (reducing 24-bit color depth to an optimized palette). For maximum file size reduction while keeping transparency, converting PNG to WebP is recommended.
What if the compressed file is larger?
Some images—especially simple graphics or pre-optimized icons—are already at their theoretical minimum byte size. Re-encoding can occasionally result in a slightly larger file. When this happens, our tool flags the item with a warning badge and provides a “Download Original” button.
Are my files uploaded to any external server?
No. All compression, bounded search iterations, and ZIP packaging run client-side inside your browser engine using the HTML5 Canvas API and Blob primitives. Your files are never sent over the Internet.