This means you can open these files in Photoshop, so if you don't have Photoshop on one device, you can still export your Photopea project and continue editing on Photoshop on another device
There are ads on the main page of the site, making for a less than stellar fit on screen. This can of course be countered by using an ad blocker in ones browser, though this does not work when using the Chrome Web Store app (which is the same as the site) as adblocker's do not work on Chrome Webstore apps.
If you save and the name you give has system weird characters like :, <, >... it'll simply refuse to save and do nothing (you'll have to give a name without those characters first).
Saving to cloud is broken in many cases
Merge down layer with mask changes actual rendering (workaround: first apply layer mask)
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Muro has a collection of preset adjustment layers that can be used to change the look of the image. They can be applied on a per layer basis or on the image as a whole.