Compress images without handing them to a remote processing server

Large images slow uploads, use more storage and can make web pages heavier than they need to be. SonoFiles Image Compressor reduces JPG, PNG and WebP file sizes inside your browser. The tool processes one image at a time to limit memory pressure, keeps the original pixel dimensions unless the browser must apply orientation, and gives you control over the trade-off between file size and visual quality.

The default Balanced mode is designed for everyday web images, email attachments, product photos and general sharing. If an image is already efficient and re-encoding would make it larger, SonoFiles keeps the smaller original file instead of presenting a larger result as a successful compression.

How to compress an image

Add one or more JPG, PNG or WebP images by selecting, dropping or pasting them.
Choose a compression goal and decide whether to keep the original format or output WebP, JPEG or PNG.
Click Compress Images. The files are processed sequentially in your browser.
Review the before-and-after sizes and download one result or a ZIP containing the whole batch.

Compression modes and when to use them

Mode	Best for	What it does
Balanced	Most photos and web images	Uses a practical lossy quality setting for JPEG and WebP while keeping dimensions unchanged.
High quality	Portfolio images and detailed photos	Uses gentler lossy compression when preserving fine detail matters more than maximum savings.
Smaller file	Email, uploads and bandwidth-sensitive pages	Uses stronger JPEG/WebP compression for a smaller result.
Custom quality	Users who want precise control	Lets you choose the JPEG/WebP quality percentage yourself.
Target file size	Upload portals with a size requirement	Searches for a JPEG/WebP quality level close to the requested KB target without shrinking dimensions.

JPG, PNG and WebP behave differently

JPEG / JPG

JPEG is designed for photographs and other images with continuous tones. Its lossy quality control can produce substantial file-size savings, which makes it a practical choice for photos, product imagery and email attachments.

PNG

PNG is lossless and is often used for screenshots, interface graphics, logos and images that need transparency. Browser PNG encoding does not use the same lossy quality slider as JPEG or WebP, so a PNG may see modest savings or no savings at all when kept as PNG. Converting a photographic PNG to WebP or JPEG can reduce size much more, but JPEG removes transparency.

WebP

WebP supports lossy compression and transparency and is widely useful for modern websites. Choosing WebP can be a strong option when you want smaller web assets while retaining alpha transparency where the source has it.

Target a file size without silently resizing the image

Some forms and upload systems require an image to stay under a specific file size. Target mode repeatedly encodes a JPEG or WebP at different quality levels and chooses a practical result near the requested target. SonoFiles does not secretly reduce the width or height to hit the number. If the requested size is too small to reach at the tool's minimum quality, the result is clearly marked as above target rather than pretending the target was met.

What happens to metadata and orientation?

Re-encoding through the browser usually removes EXIF and other embedded metadata. This often contributes to a smaller file, but it also means camera information, GPS data and other metadata should not be expected to remain. Modern browsers normally apply photo orientation while decoding, so the visible result should stay upright even when the original relied on an EXIF orientation flag.

Private Browser-Based Image Compression

The compressor does not need to upload your selected images to a SonoFiles processing server. Decoding, canvas rendering, encoding and ZIP creation happen on your device. Your browser still needs normal network access to load the SonoFiles page itself, but the image bytes selected for this workflow are processed locally.

Limits designed for useful real-world batches

You can select up to 100 images. Each file can be up to 100 MB, and the total selected batch can be up to 300 MB. For best reliability, especially on phones or low-memory computers, keep the batch at or below 200 MB. SonoFiles processes images sequentially rather than decoding the entire batch at once.

An image can require far more memory after decoding than its compressed file size suggests. For that reason, images above 100 megapixels or 32,768 pixels on either side are rejected as technical browser-safety measures. Images below those limits are accepted when the browser can decode them. This is not a paid limit: there is no account, watermark, daily quota or paid size unlock.

Useful image-compression workflows

Website performance: reduce photo weight before adding images to landing pages, blogs or ecommerce listings.
Email and messaging: make camera photos easier to attach and send.
Upload limits: use target-size mode when a portal requires a JPEG or WebP below a particular KB threshold.
Batch preparation: compress a folder of product or article images together and download one ZIP.
Privacy-sensitive work: process local images without intentionally sending their contents to a remote compression service.

Image Compression Problems and Practical Fixes

Why did my PNG barely get smaller?

PNG uses lossless compression and can already be highly optimized. If smaller size matters more than keeping the exact format, try WebP. For photographic PNG files, JPEG may also be much smaller if transparency is not needed.

Why was the original kept?

If the browser-generated file is larger than the original, SonoFiles keeps the smaller source instead. The tool does not count a larger output as a successful compression.

Why can a target size be missed?

Target mode does not resize dimensions. A detailed high-resolution image may still be larger than the requested target even at the lowest allowed quality. Use a larger target or use the live Image Resizer when reducing dimensions is appropriate.

Why are GIF, SVG or HEIC not accepted here?

This compressor currently focuses on JPG, PNG and WebP so it can keep the workflow predictable in the browser. GIF can be animated, SVG is vector-based and HEIC support varies by browser; treating those formats as ordinary raster photos could produce misleading or destructive results.

Compression and Resizing Solve Different Problems

Compression changes how pixel data is encoded; resizing changes how many pixels exist. A 6000 × 4000 photograph can remain large even at decent compression because it contains 24 million pixels. If the image will only be shown at 1200 pixels wide, resizing first can reduce bytes more cleanly than forcing very low JPEG quality. For upload forms, read both the pixel-dimension and file-size requirements before deciding which operation should happen first.

Why a 'Compressed' Output Can Sometimes Be Larger

An already optimised source can be more efficient than a new encoding. A PNG can also behave poorly when forced through an unsuitable format path. The hardened compressor keeps the original when a newly encoded file would be larger or equal without adding value. Honest compression means refusing to report a larger file as a successful reduction. The goal is a meaningfully smaller result that still looks appropriate for the intended use.

Target-Size Mode Is for Maximum Limits, Not Perfect Equality

Some portals require an image below a specific KB threshold. JPEG and WebP encoders produce discrete sizes, so an exact byte count cannot always be hit perfectly. Aim a little below the published maximum and test the result in the destination system. If quality search alone cannot reach a strict target because the source dimensions are huge, Image to Exact KB can also reduce dimensions under controlled rules.

How to Compare Compression Quality Properly

Inspect the result at the size it will actually be used. For photographs, check fine texture, gradients, hair and foliage. For screenshots, zoom into small text and icons. For transparent graphics, make sure the output format still supports alpha. Compare file-size saving with visible change. If a more aggressive setting saves only a tiny amount, keep the cleaner result. File size alone is not a quality score.