Use Photopea on the web
This is a web app. Open the official website in your browser.
Open official websiteAbout Photopea
Photopea is an image editor that runs in a web browser. It can handle simple changes such as resizing a picture as well as more involved work with layers, selections and graphics. You can open it on a phone without installing a separate desktop program.
The detailed workspace is better suited to a large screen and precise controls. On a phone, it may be useful for an occasional edit, while a focused tool can be easier for a quick resize or conversion.
Photopea's documentation explains that editing runs on your device. Start with a copy of your image, learn how its open and save commands work, and check the exported format before closing the page.