Compress images without losing quality
Drag the images into Images by Edmund and press Export. With the format left on Same as source it makes each file smaller without altering how it looks: a JPEG is rebuilt from the data it already contains, and a PNG is recompressed. Not one pixel changes. If the result would be larger than your original, it keeps your original.
macOS 15 or later. Apple silicon Mac. Version 1.1.0, out 11 October 2026. What’s new.
Free, with nothing to unlock and no account.
Try it on one file first
Drop a PNG or a JPEG in and get the same file back, usually smaller. A PNG is recompressed and a JPEG is repacked from the frequency data it already holds, so not one pixel changes either way, and where there is nothing left to save it says so and leaves your file alone rather than handing you a copy of it. The before and after are both real numbers rather than an estimate. It happens in this tab, on your own machine, and nothing is uploaded.
Lossless compression, step by step
- Drag the images inA folder is the normal case. Leave the format menu alone, on Same as source, which is the setting that means make this smaller without changing what it is.
- Check the numbers on the cardsEach card shows the before and after. Files that have already been optimised will barely move, and that is the honest answer rather than a fault.
- Press ExportWrite beside the originals to compare them, or replace the originals once you trust it. Replacing puts the old files in the Trash, never straight to deletion.
A JPEG is rebuilt from its own coefficients, and a PNG has its filters searched
Lossless means different things in the two formats and the app does both properly. A JPEG is not decoded to pixels and re-encoded, which would lose detail. It is rebuilt from the frequency coefficients already stored in the file, rearranged into a more efficient arrangement, so the decoded image is bit for bit what it was. For PNG, most writers pick each row's filter with a thirty year old heuristic; this one tries the alternatives and keeps whichever actually compresses smallest, then compresses it with libdeflate at the slowest setting it has. It also drops a transparency channel that turns out to be completely opaque, which design tools write constantly and which costs about a quarter of the file. Every pixel is checked before that happens, because 254 is not opaque.
Why not just use a converter website?
Optimising is the step you want to run over everything, repeatedly, as a habit. Anything involving an upload stops being a habit within a week, because the friction lands every single time.
The other half is trust. A site that promises lossless compression gives you no way to verify it, and several of the popular ones quietly re-encode instead. Running it locally means the original is still sitting there next to the result, and you can compare them whenever you like.
Questions
Does lossless compression really not change the image?
Correct. Decode the file before and after and you get identical pixels. What changes is how those pixels are stored, not what they are. It is a different operation from lowering a quality setting, which does throw detail away.
How much smaller will my files get?
It depends entirely on what made them. Files straight out of a design tool or a camera often have a lot to give; files that have already been through an optimiser have almost none. The cards show the real figure per file before you commit.
What if the compressed file is bigger?
Then the app keeps yours. It compares the result against the original and writes whichever is smaller, so running it over an already optimised folder cannot make things worse.
Is this the same as lowering the quality?
No, and the difference matters. Lowering quality discards detail to save space and cannot be undone. This rearranges what is already there. Both are available in the app; Compression under Options is where you choose.
Other things it does
There is a full list on the Images by Edmund product page, along with what else the app does.
Get Images by Edmund.
Free, and it does the other eight jobs too. Two ways to get it when it lands: the Mac App Store, or straight from here.
macOS 15 or later. Apple silicon Mac. Version 1.1.0, out 11 October 2026. What’s new.