Compress images on your Mac under 1 MB, 500 KB or 200 KB, without uploading
By Himanshu Ranjan · Updated 8 November 2026
To compress an image on a Mac with FileDial, select it in Finder, hold the right Option key and choose Compress › Compress for a smaller copy that looks the same, or a size target such as Compress › Compress under 500 KB. The smaller copy is saved beside the original, which is not changed. It works on many images at once, entirely on your Mac.
How to do it with FileDial
- Select the images in Finder (one or hundreds).
- Hold right ⌥ to open the dial.
- Choose Compress › Compress, or a target such as Compress › Compress under 200 KB.
- Check the result card for the size before and after.
- Use Undo if you want to try a different target.
Your original file stays untouched. The result is saved beside it, and every result has Undo.
Which option to pick
| Tool | Use it when |
|---|---|
| CompressCompress | General shrinking: a smaller copy that looks the same, when you have no specific size limit. |
| Compress under 2 MBCompress | For upload forms or email services with a 2 MB cap; new copy beside the original. |
| Compress under 1 MBCompress | For portals that cap images at 1 MB; new copy beside the original. |
| Compress under 500 KBCompress | For stricter limits such as some application or listing forms; new copy beside the original. |
| Compress under 200 KBCompress | For the tightest limits, such as ID photos or signature uploads; new copy beside the original. |
| Compress to size…Compress | When your limit is not one of the presets: set your own target size and get a new copy beside the original. |
How image compression works, and why exact targets matter
Most photos are compressed with lossy formats such as JPG. The encoder throws away detail your eye is unlikely to miss, and a quality setting decides how much. Lower quality means a smaller file, and past a certain point you start to see blocky edges, banding in skies and smeared texture. The other lever is pixel dimensions: a 12-megapixel photo shown at phone size carries far more data than anyone will see.
Upload forms rarely care about either lever. They state a hard limit, such as 1 MB or 200 KB, and reject anything bigger. Guessing a quality slider value and checking the size by hand is tedious, especially across a folder. Size-target tools exist to do that search for you: you name the limit and get a copy that fits under it.
PNG screenshots and graphics are a different case. PNG is lossless, so a detailed screenshot can be surprisingly large. Converting it to JPG first, then compressing, is often the simplest route to a small file.
- No limit given: use Compress.
- A stated limit: pick the matching Compress under… target.
- A screenshot that will not shrink: convert to JPG first.
Why not use an online image compressor
The images people need to squeeze under a limit are often the sensitive ones: passport photos, ID scans, signatures and documents for visa, job or bank applications. An online compressor needs those files uploaded first. In July 2024 Cybernews reported that two online PDF services had left their Amazon S3 storage open, exposing 89,062 uploaded files including passports, IDs and certificates, and said the providers did not respond.
There is also the risk in what comes back. The FBI Denver Field Office warned in March 2025 that free online converter sites are increasingly used to deliver files carrying malware, and to scrape personal data. FileDial compresses on your Mac, so nothing is sent to a server, and every tool works with Wi‑Fi off.
Other ways to compress images on a Mac
For a single JPG, Preview works: open the image, choose File › Export, pick JPEG and drag the Quality slider down, and the dialog shows an estimated file size. Reducing dimensions with Tools › Adjust Size also cuts the file size a lot. On recent macOS versions, Finder's Quick Actions › Convert Image can save a smaller size of selected images.
Those tools make you guess quality per image. FileDial is better when you have a fixed limit like 500 KB, many images to process at once, or you want to compare sizes on the result card and Undo a pass that went too far. Recipes can also chain a resize and a compress so a whole folder is handled the same way.
Questions
Does compressing replace my original image?
No. Every Compress tool saves a new copy beside the original. The original stays as it was, the result card shows the size before and after, and Undo removes the copy.
How do I get a photo under 200 KB for an application form?
Select the photo in Finder, hold right ⌥ and choose Compress › Compress under 200 KB. You get a new copy aimed at that limit beside the original, without uploading the photo anywhere.
Can I compress a folder of photos at once?
Yes. Select all the images and run one Compress tool; it runs on every selected file. Recipes and watched folders can also apply the same compression to anything you drop into a folder.
Does it work offline?
Yes. Every FileDial tool runs on your Mac and works with Wi‑Fi off. Files, file names and paths are never sent anywhere. The only network traffic is a licence check and optional anonymous usage counts you can switch off.