Reduce file size online - images, videos, PDFs and audio

Use KitDevs to reduce file size in your browser without uploading files. Pick the file type, choose the right tool, and download a smaller output made locally on your device.

Images

Images are often large because cameras and design tools export more pixels and quality than a website, email, or chat message needs. Compress JPG photos by lowering JPEG quality, compress PNG graphics by choosing the right output format, or use WebP when the smallest web file matters.

For images that are physically too large, combine compression with resizing. A 4000 x 3000 photo has far more pixels than most screens need. Reducing dimensions first can cut file size before quality settings are even applied.

• Use Compress JPG online for photos.
• Use Compress PNG online for screenshots and transparent assets.
• Use Resize image online when dimensions are the real problem.

Videos

Videos are large because they store many frames per second plus audio. Size depends on duration, resolution, frame rate, codec, and bitrate. Reducing bitrate or resolution can make an MP4 much easier to share.

KitDevs uses FFmpeg.wasm locally for video compression. This takes more CPU time than image work, but it avoids sending private recordings to a server.

• Use Compress video online for MP4, MOV, AVI, and MKV.
• Use Compress MP4 online for a focused MP4 workflow.
• Use Convert video to MP3 when only the audio track is needed.

PDFs

PDF size depends on embedded images, fonts, object streams, and scan resolution. Text-heavy PDFs may already be small. Scanned PDFs and design exports usually have more room for reduction.

KitDevs can optimize PDF structure and, for image-heavy documents, create smaller page images. This is useful for email limits, document portals, and web publishing.

• Use Compress PDF online for attachments and scanned files.
• Use Free PDF tools online for merge, split, rotate, and conversion tasks.

Audio

Audio size depends on duration, codec, bitrate, channel count, and sample rate. MP3 and M4A are much smaller than WAV because they use lossy compression. If a video only needs to be shared as sound, extracting MP3 can reduce size dramatically.

KitDevs uses FFmpeg.wasm for audio extraction and conversion. The result is created locally and downloaded from your browser.

• Use Convert MP4 to MP3 for video audio extraction.
• Use Convert video to MP3 for MOV, AVI, MKV, and MP4 sources.

Why browser-based compression protects your files

Traditional online compressors start by uploading the file. That can be fine for public assets, but it is not ideal for private photos, contracts, invoices, scans, or internal recordings. Browser-based tools change the model: the code comes to your device, then your device processes the file.

KitDevs does not need accounts, upload queues, or server storage for the file. This makes it easier to use a compression tool for sensitive work without adding another data processor to the workflow.

Which format compresses best?

There is no single best format for every file. The best choice depends on the content and where it will be used. Photos, screenshots, scanned PDFs, and audio recordings all respond to different compression methods.

Related KitDevs guides

• Compress PDF online - reduce document size
• Compress video online - reduce MP4, MOV, AVI, and MKV files
• Convert file format online - conversion pillar for format changes

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Frequently asked questions