Compress PNG Image
Reduce the file size of your PNG images by optimizing quality while keeping visual fidelity.
Compress PNG files without losing transparency or sharp edges
PNG compression works by re-encoding the image data at a lower quality level, or by applying lossless deflate optimization that removes redundant bytes without changing any pixel values. SimpleSize processes your file in memory on the server and returns the smaller PNG immediately. Files are never written to disk or stored after the response is sent.
The tool accepts PNG files up to 40 MB each and lets you upload multiple files in one session. You get a side-by-side view of the original size versus the compressed size, so you can judge the result before downloading.
When to shrink a PNG versus switching formats
PNG is a lossless raster format that stores an alpha (transparency) channel. That makes it the right choice for logos, icons, UI screenshots, and any graphic that needs a transparent background. The tradeoff is file size: PNG encodes every pixel precisely, so files are often larger than their JPG or WebP equivalents.
Use this tool to reduce PNG file size when you must stay in the PNG format. Common reasons include:
- The image has transparency that would break in JPG.
- A platform or CMS requires PNG specifically.
- You need lossless output but the current file is bloated with metadata or sub-optimal encoding.
- You are preparing icons or sprites where pixel-perfect edges matter.
For photographs without transparency, compressing as JPG or compressing as WebP will typically produce a much smaller file at equivalent visual quality. PNG compression is most effective on graphics with large flat-color areas, not on photos with complex gradients.
How to use the PNG size reducer
The workflow is straightforward and requires no account or login.
- Open the tool at simplesize.app/en/compress-png .
- Drag and drop your PNG files onto the dropzone labeled "Drop image files here or click to browse", or click it to open a file picker. Multiple files are accepted in one batch.
- Move the Quality slider to your target level. The range is 10% to 100%, with 82% as the default. Lower values produce smaller files with more visible quality reduction.
- If you need zero quality change, open "Advanced compression controls" and enable "Keep lossless compression (PNG/WEBP only)". This mode removes redundant data without altering any pixel values.
- Click "Compress Images". A progress bar labeled "Processing images..." appears while the server re-encodes your files.
- Review the results. Each output shows the original size, compressed size, dimensions, and a download button.
Lossless mode is the right choice when you are delivering assets to a client or publishing a design where any visible artifact is unacceptable. Quality slider compression gives you more aggressive size reduction at the cost of minor pixel-level changes that are often invisible at normal viewing sizes.
What affects how much smaller your PNG gets
The compression ratio you see depends on the content of the image, not just the quality setting. PNGs that contain large areas of a single color, simple geometric shapes, or flat UI elements compress more than photographs encoded as PNG. The lossless toggle shrinks files by optimizing the internal encoding; the quality slider goes further by allowing lossy re-encoding.
Key factors that influence the output size:
- Image content complexity: Flat-color graphics shrink more than photographic PNG files.
- Quality slider value: Values below 82% produce progressively smaller files with increasing pixel-level changes.
- Lossless mode: Reduces size without any quality change, but the savings are smaller than lossy compression.
- Original encoding quality: A PNG that was already well-optimized will yield less additional reduction.
- Transparency: The alpha channel is preserved in all modes, so transparent areas are never flattened.
FAQ
PNG compression re-encodes the image data using a deflate algorithm. In lossless mode, the encoder finds a more efficient way to represent the same pixel values, so no information is lost. In lossy mode (controlled by the Quality slider), the encoder reduces color precision or merges similar tones before applying deflate, which allows larger file size reductions at the cost of minor pixel-level changes that are often invisible at normal screen sizes.
No. The alpha channel that carries transparency data is preserved in both lossy and lossless modes. The re-encoding process keeps the channel intact, so your transparent areas remain fully transparent in the output file. This is one of the main reasons to stay in PNG format rather than converting to JPG, which does not support an alpha channel at all.
The Quality slider applies lossy compression. It reduces color information before re-encoding, which means some pixel values change. Lower slider values mean more reduction and more visible change. Lossless mode, enabled via "Keep lossless compression (PNG/WEBP only)", applies only structural optimizations to the file encoding. No pixel values change, but the file size reduction is smaller. Use lossless when visual fidelity must be guaranteed; use the slider when you want the smallest possible file and can accept minor quality changes.
Each PNG file can be up to 40 MB. The tool accepts multiple files in a single session, so you can process a batch of images at once. If a file exceeds the limit, the tool will indicate an error for that specific file while still processing the others in your batch.
No. Files are processed entirely in memory and are never written to disk. Once the server returns the compressed result to your browser, the data is discarded. No login is required, and no account is created, so there is no persistent storage associated with your session.
JPG compression uses a discrete cosine transform that discards high-frequency detail and cannot store an alpha channel. The output is always a flat-background image. PNG compression, whether lossy or lossless, keeps the full alpha channel and produces output that still renders transparency correctly. For photographs, JPG compression typically achieves a smaller file at equivalent perceptual quality. For graphics with transparency or sharp edges, PNG is the appropriate format to stay in.
Two common reasons explain limited reduction. First, if the original PNG was already well-optimized, there is little redundancy left to remove. Second, photographic images encoded as PNG contain too much pixel variation for deflate compression to find patterns, so the savings are small regardless of settings. In that case, consider converting the image to WebP or JPG, which use algorithms designed for photographic content and will produce a significantly smaller file.
The default of 82% is a practical starting point for most web use cases. At this level, the pixel-level changes introduced by lossy re-encoding are generally not visible at normal browser zoom. For icons or logos where brand color accuracy matters, try 90% or higher, or use lossless mode. For background textures or decorative graphics where file size is the priority, values between 60% and 75% often work well. Always review the result at full size before publishing.
Yes. The dropzone accepts multiple PNG files at once. All files in the batch share the same Quality slider and lossless toggle settings. Results are shown individually, so you can see the size reduction for each file and download them separately. This is useful when preparing a set of icons or UI assets that all need the same compression level applied consistently.
No. The tool reduces file size through re-encoding, not by resizing. The output image has the same pixel dimensions as the original. The results panel shows the dimensions alongside the original and compressed sizes so you can confirm this before downloading.
Yes, the PNG compression tool is free and requires no account or login. You can upload files, adjust settings, and download results without any registration step. The general image compressor on SimpleSize covers additional formats including JPG, WebP, GIF, AVIF, HEIC, and TIFF, all under the same free model.
WebP supports both an alpha channel and more efficient compression algorithms than PNG, so it can produce smaller files while preserving transparency. If your target platform and browsers support WebP (which all major modern browsers do), it is often a better choice for web delivery. PNG remains preferable when the platform requires it explicitly, when you need maximum compatibility with older software, or when you are storing source assets that will be re-edited later.