Because PNG is a lossless format (meaning better quality), Firefox tries to save that format whenever possible. However, there are some circumstances when screenshots will be saved as JPGs. This is mostly dictated by size restrictions.

While there is no builtin option to choose the desired screenshot output file, PNGs can easily be converting into JPGs using free online conversion tools.

Hope this helps.

Some picture viewers can do this.

Thank you for your time and expertise, FredMcD and Wsley.

Unfortunately this does not solve my problem so, please, allow me to ask 2 more questions:

1. Is there a way to recommend to Mozilla to revert back to JPG or to add an option to select the preferred file type?

2. Win10 has a JPG screenshot tool but it does not allow cropping. Can you recommend addons that offer both cropping and JPG?

Again, thank you both for your time.

Tommaso

If you want to leave feedback for Firefox developers, you can go to the Firefox Help menu and select Submit Feedback... or use this link. Your feedback gets collected by a team of people who read it and gather data about the most common issues.

Use a web search to find what you want.

There are tons of free screenshot add-ons for Firefox, like Lightshot. However, most save in PNG format because of the significant quality improvement.

In fact, just a few months ago there were multiple complaints about Firefox saving screenshots as JPGs in the first place because of the low quality.

The only other thing that I can recommend is a free program called FastStone Photo Resizer. I use it myself. It's good for changing files from PNG to JPG and I use it all of the time for this purpose. You could take screenshots that Firefox saves and run them through this program.

Out of curiosity, is there a particular reason that you want the images in JPG format instead of the default PNG?

Dear Wesley,

Again, thank you for your time. I do appreciate it.

I prefer JPG because I often send screenshots by emails (Outlook 365) that does not allow me to drag and drop PNG files into the email. I have to open, then save as JPG and then I can drag/drop.

Using programs as FastStone will only make the process even more complicated. I would like Mozilla to offer the option of convenience VS quality, by adding the option to save in the oreferred format.

Tommaso

If you want to leave feedback for Firefox developers, you can go to the Firefox Help menu and select Submit Feedback... or use this link. Your feedback gets collected by a team of people who read it and gather data about the most common issues.

Dear Fred, thank you. I just left my feedback.

ascanio1 said

My screenshot tool saves both "full page" and "visible" in .png. A short while ago it used to save both in jpg and now I would like to revert to jpg.

Hi Tommaso, do you mean the built-in Firefox Screenshot tool (on the ••• menu "Take a screenshot") or a different tool?

The built-in tool may save larger images with JPEG compression automatically, but does not provide a choice.

I use the following extension for one-click full-page screenshots, and in its options, you can select either PNG, JPG, or let you choose each time. However, it doesn't let you make a selection and capture only the selection:

https://addons.mozilla.org/firefox/addon/savescreenshot/

From the Options screen:

Thank you. I appreciate your time and expertise.

If anyone knows of add ons that allow to select/crop + save in JPG it would be very much appreciated

Hi, take a look at this - which I use when the Firefox built-in screenshot tool isn't enough - https://addons.mozilla.org/en-US/firefox/addon/nimbus-screenshot/

I think it does everything you want - and more!

You can select JPG in its Options > Settings, within the add-ons Manager (Ctrl+Shift+A), or click its button on your toolbar then the gear wheel button at the bottom of the dropdown.

Interesting:

I testes the clipboard with a screenshot Copy and I see these flavors: image/png, image/jpeg, image/jpg The image/jpg flavor doesn't seem to have any data. Using the image/jpeg flavor gives me a file with a JFIF code. And opening the file as a data URI allows to save the file as a .jpg file.

Possible JavaScript code that you can run via the command line in the Browser Console.

• https://developer.mozilla.org/en-US/Tools/Browser_Console

var cb = Services.clipboard;
var ps = Services.prompt;
var flavor = "image/jpeg"
var trans = Cc["@mozilla.org/widget/transferable;1"].createInstance(Ci.nsITransferable);
trans.init(null);
trans.addDataFlavor(flavor);
var str = {}, dat = "";
cb.getData(trans,cb.kGlobalClipboard);
try {trans.getTransferData(flavor, str, {})} catch(e){alert(e.toString().substr(0,800))}
if (str && str.value){
dat = str.value.data;
dat = "data:" + flavor + ";base64," + btoa(dat);
var obj = new Object; obj.value = dat;
ps.prompt(null, "CLIPBOARD", "< \"" + (dat ?"":"NO \"") + flavor + "\" DATA from CLIPBOARD >", obj, null, {});
}

Scribe said Hi, take a look at this - which I use when the Firefox built-in screenshot tool isn't enough - https://addons.mozilla.org/en-US/firefox/addon/nimbus-screenshot/

Thank you. This solves my problem. I feel really stupid now because I actually had Nimbus installed before I started using Firefox proprietary screenshot tool and disinstalled Nimbus! I completely forgot about Nimbus. It's a bit more time consuming but it can be somewhat set to partially automatic.

Again, thank you.

cor-el said

Interesting: I testes the clipboard with a screenshot Copy and I see these flavors: image/png, image/jpeg, image/jpg The image/jpg flavor doesn't seem to have any data. Using the image/jpeg flavor gives me a file with a JFIF code. And opening the file as a data URI allows to save the file as a .jpg file.

---

Possible JavaScript code that you can run via the command line in the Browser Console.

• https://developer.mozilla.org/en-US/Tools/Browser_Console

var cb = Services.clipboard;
var ps = Services.prompt;
var flavor = "image/jpeg"
var trans = Cc["@mozilla.org/widget/transferable;1"].createInstance(Ci.nsITransferable);
trans.init(null);
trans.addDataFlavor(flavor);
var str = {}, dat = "";
cb.getData(trans,cb.kGlobalClipboard);
try {trans.getTransferData(flavor, str, {})} catch(e){alert(e.toString().substr(0,800))}
if (str && str.value){
dat = str.value.data;
dat = "data:" + flavor + ";base64," + btoa(dat);
var obj = new Object; obj.value = dat;
ps.prompt(null, "CLIPBOARD", "< \"" + (dat ?"":"NO \"") + flavor + "\" DATA from CLIPBOARD >", obj, null, {});
}

Thank you. I am certain that this would sove my problem but I am not sufficiently proficient to understand what a Java Script is or does and installing add ons is as far as I can go...

'(

But thank you for helping me, I appreciated it!