JPG vs PNG vs WEBP comes down to the picture
Photos go to JPG. Keep PNG when the empty pixels matter. WEBP is smaller, but whether it opens on the other end is a separate question. Those three lines cover most cases. When you do need to switch, use Retype format, choose a target, then look at the result once.
Photo: JPG. Transparency: PNG. WEBP: ask first. If unsure, send JPG.
Photos mostly go to JPG
Shots from a phone or a camera, frames full of gradients: JPG. It holds up better at the same file size, and the price is that it re-encodes by quality, which is lossy. In Shrink file the quality slider only runs from 40 to 95, default 78. Pull it down and the file gets smaller while hair and letter edges soften. Push it up and more detail survives, at a larger size. There is no setting called lossless.
JPG also has no transparency layer. Once a picture with an empty background becomes JPG, that emptiness has to be filled with a color. Shrink file fills it with white, and that page has no background picker. To choose the color yourself, go to Make JPG; it offers the picker, and the quality slider is the same 40 to 95.
Keep PNG when transparency matters
Screenshots, logos, interface shots with text, and anything that still needs an empty background stay in PNG. A screenshot saved as PNG keeps a clean edge instead of a dirty halo. To make a PNG smaller, Shrink file reduces the number of colors according to quality. The slider never reaches 97, so this page will not take the keep-every-color path. Cut too many colors and gradients start to band.
- Photos, faces, landscapes with gradients: JPG.
- Screenshots, logos, anything still transparent: PNG.
- For the web, once you know the other side can open it: WEBP.
- Short loops with few colors: GIF, frames and their timing intact.
WEBP depends on what opens it
WEBP is often smaller at the same look, and web pages and recent browsers read it. It does not open everywhere. Some older viewers and some upload forms accept only JPG or PNG, and your file comes back rejected or silently re-saved. Before sending to a person, think about the app on their side. If you are not sure, send JPG and spare them an install.
To turn a picture into WEBP, use Retype format. That page swaps between JPG, PNG, WEBP, GIF, BMP, TIFF, SVG and ICO. Saving to SVG wraps the pixel image inside an SVG; it does not redraw the photo as vectors. Only a file that was already SVG, run through the minify in Shrink file, stays vector.
Every conversion re-encodes
JPG to PNG and back to JPG means the picture was decoded twice and encoded twice. Detail lost on the first pass does not return on the second. The file can even grow, because PNG stores a different kind of data. If the goal is a smaller file, do it last, and take the short route.
A common case: one picture needs both a new format and a smaller size. Convert first in Retype format, then set quality in Shrink file, rather than bouncing between the two pages. The longest-edge field in Shrink file defaults to 0, which leaves width and height alone. Type a positive number and only a long edge above that number is pulled down; small pictures are not enlarged and nothing is cropped.
Changing the format is not changing the wrapper. The picture is recomputed each time.
Where transparency goes
A transparent PNG turned into JPG gets solid color where the emptiness was. For white, Shrink file already fills white. For another color, pick it in Make JPG. The reverse does not happen: JPG to PNG keeps white pixels white, it does not make them empty. Emptying a background for real belongs to Lift the subject, which exports a PNG with transparency. The first run downloads a recognition model to this device; the work still happens on this device.
When a page opens, the visit is counted by 51.LA. What is counted is that someone opened the page, not your image file. Pictures are not uploaded to ReadyIMG, and there is no sign-in or account server that receives them. That boundary is written down in How files are handled.
Three looks before you send
- What opens it on the other end. Old software and upload forms: send JPG.
- Whether transparency survived. Save as JPG and it is gone.
- Whether the file is small enough and still readable. If it is mushy, step the quality back up and run it again.
Up to 40 files at a time, and one step can be run start to finish before you download the pack. The queue lives only in this open tab; refresh or close it and anything you did not download is gone. The originals stay in their folder unless you replace them yourself.
If nothing is loaded yet, go back to the bench, drop the picture in, then open Retype format. Before you change a format, settle one question: what will that person open it with.