Hit an exact file size
Set a target in KB or MB and the app compresses until it fits, showing the before and after size as it goes.
Tool
Image Compressor & Converter
Shrink photos to an exact file size, or convert between JPG, PNG and WebP in batch — on your phone, nothing uploaded.
Why OneBox for compression
Batch convert formats
Convert between JPEG, PNG and WebP in bulk. Tune quality and decide whether EXIF metadata is kept or stripped.
Resize the way you think
By exact width and height, by percentage, or capped to a maximum dimension — then apply it to a whole folder at once.
How it works
- 1
Pick your images
Select a single photo or a whole batch from your gallery.
- 2
Choose a goal
Compress to a target size, convert the format, or resize. The estimated result is shown before you commit.
- 3
Export
Save back to your gallery or share straight away. Originals are never modified.
AI agent
Or just say it
Tell the built-in agent what you want in plain English. It picks the right tool, runs it, and reports back — you never leave the chat.
›
Compress every screenshot in this folder to under 500 KB›
Convert these PNGs to WebP at quality 85›
Resize these photos to 1920px wide and keep the EXIF dataCommon questions
Does it need an internet connection?
No. Compression, conversion and resizing all run locally on your phone. Your images never leave the device.
Which formats are supported?
JPEG, PNG and WebP, for both input and output. You can also choose whether EXIF metadata is preserved.
Can I hit an exact size such as 500 KB?
Yes — that is what the compress-by-size mode does. You set the target, it works out the quality needed, and shows you the result in KB.
Will my original photos be changed?
No. Results are always written as new files, so your originals stay exactly as they were.
Is there a limit on how many images I can do?
No. Batch mode takes as many as you select; the only limit is your phone's storage.
Get OneBox free
90+ tools, free, no ads. All processing happens on your device. Open source under Apache-2.0.