Can I compress PDF, PNG, and JPEG files in the same session?

Yes. You can add multiple files of different types to Minifiles.io in a single session. Each file is processed with the appropriate engine.

Which format compresses the most?

Scan-heavy PDFs typically see the largest reductions — 60–90% with the Maximum preset (Pro). JPEG photographs also compress significantly — 50–70% at quality 80. PNG logos and screenshots compress by 50–80%. Text-heavy PDFs and already-optimised images compress the least.

Is there a file size limit?

There is no hard file size limit imposed by Minifiles.io, but very large files (above 100–200 MB) may exhaust browser memory, particularly on mobile devices. Performance depends on the available RAM on your device.

Does compression reduce image dimensions?

For JPEG and WebP, images larger than 4096 px are scaled down by default, and on the Pro plan you can set your own maximum dimensions. For PNG, compression does not change dimensions. For PDF, compression reduces image resolution within the document but does not change the page dimensions.

Does Minifiles.io upload my files to a server?

No. All compression runs locally in your browser using JavaScript and WebAssembly. Your files never leave your device.

Can I use Minifiles.io offline?

Not reliably. The compression engines are downloaded on demand when you use each tool, so you need an internet connection. Your files are still processed locally and are never uploaded.

Practical Guide: Compress PDF, PNG and JPEG Files Locally

Why compress files locally instead of uploading to a service?

Server-based compression tools require you to upload your file to a remote server. The server processes the file and returns a download link. This is convenient but has three drawbacks: privacy (your file reaches a third party), speed (upload and download time adds latency), and dependency (the service must be available and your file must be within its size limits). Local browser-based compression eliminates all three: the file never leaves your device, and compression starts immediately without an upload round-trip.

How Minifiles.io processes files locally

Minifiles.io uses JavaScript and WebAssembly to run compression algorithms inside the browser tab. For images, the compression engines (UPNG.js for PNG, Compressor.js for JPEG and WebP, Gifsicle for GIF) are loaded as JavaScript modules. For PDFs, a WebAssembly worker is loaded into the browser. When you add a file, it is read from your device into browser memory, passed to the appropriate engine, processed, and returned as a downloadable output. No file data is sent to any external server at any point.

Compressing PDF files: settings and results

Drop a PDF onto the PDF tab in Minifiles.io. The default preset is Balanced (150 DPI — a good balance for email and general sharing), and it is the one available to free users and guests. Pro unlocks all four: Maximum (smallest file, 72 DPI images — ideal for web sharing and email), Balanced, High Quality (300 DPI — suitable for printing) and Lossless (300 DPI — preserves maximum quality for professional use). After compression, the comparison panel shows original and compressed sizes. Password-protected PDFs cannot be processed. Expected results: scan-heavy PDFs can be reduced by 60–90%; text-heavy PDFs typically see 10–30% reduction. If you need a specific target size, try our compress PDF to 100 KB or compress PDF to 1 MB tools.

Compressing PNG files: settings and results

PNG files are compressed using UPNG.js, which applies colour quantisation — reducing the number of distinct colours in the image to produce a smaller file while maintaining the PNG format. The quality slider controls how aggressively colours are reduced: high quality preserves near the full colour range with modest size reduction; low quality produces a smaller file with some visible posterisation on smooth gradients. PNG compression in Minifiles.io is most effective on images with large flat-colour areas (logos, diagrams, screenshots) and less effective on complex photographs with many colour gradations. Expected results: logos and screenshots can be reduced by 50–80%; detailed photographs typically see 20–40% reduction. Try our dedicated compress PNG tool for the fastest workflow.

Compressing JPEG files: settings and results

JPEG files are compressed using Compressor.js, which re-encodes the image at the selected quality level. The quality slider controls the JPEG compression ratio: higher values preserve more detail; lower values produce smaller files with more visible compression artefacts. On the Pro plan you can also set maximum width and height dimensions to resize the image during compression — useful for reducing very large photos to a standard web resolution. EXIF metadata handling is configurable: you can strip metadata (reducing file size further and removing location data) or retain it. Expected results: a smartphone JPEG at high quality can typically be reduced by 50–70% at quality 80 with no visible artefacts on screen. Try our dedicated compress JPEG tool for the fastest workflow.

Compressing WebP and GIF files

WebP files are compressed using Compressor.js with lossy re-encoding. WebP is already an efficient format, so gains are more modest than JPEG — typically 15–30%. GIF files are compressed using Gifsicle via WebAssembly, which optimises the colour palette and frame data in animated GIFs. Frame-heavy animations with many colours see the largest reductions — typically 20–40%. Simple GIFs with few colours and frames compress less. For all image formats, our compress image tool provides the fastest workflow.

Comparing original and compressed files

Minifiles.io includes a side-by-side comparison viewer for images. You can drag a divider across the image to compare the original and compressed versions visually. For PDFs, the comparison panel shows the original and compressed file sizes as numbers. Always review the output before downloading — if the quality reduction is too visible, increase the quality setting and recompress.

Processing multiple files

Minifiles.io accepts multiple files in a single session. You can drag several images or PDFs onto the upload zone at once. Each file is processed independently using the same settings. Download links appear for each file individually, or you can download all compressed files as a ZIP archive. This makes it practical to process a batch of images from a photo session or a folder of documents without uploading anything to an external service.

Tips for getting the best results

For PDFs: start with the Balanced preset; on Pro, switch to Maximum only if the file is still too large after Balanced compression. For PNG: if the output quality looks too low, increase the quality slider; for logos and flat-colour images, even low quality settings often produce excellent results. For JPEG: quality 75–85 is the sweet spot for most use cases — smaller than the original with no visible artefacts on screen. For all formats: use the comparison viewer before downloading to confirm the result meets your needs.

What Minifiles.io does not do

Minifiles.io does not convert documents to or from Office formats (e.g. PDF to Word); converting images to WebP is free, while JPEG or PNG output is a Pro feature. Converting PDF pages to JPG or PNG is a separate PDF to image tab, and images can be combined into a PDF in the Merge tab. It does not strip PDF metadata. It does not encrypt files as part of compression — though it does support separate local PDF password protection via the Protect tab, and separate tools to merge and split PDFs. It does not process video files. Its focus is on reducing the size of the formats it supports: PDF, PNG, JPEG, JPG, WebP, and GIF.