The Firefox web browser is shortening the interval between new version releases. The Extended Support Release, or ESR, will remain on an annual schedule.

According to a report by The Register, Mozilla engineering director Sylvestre Ledru (실베스트르 르드뤼) said on a developer mailing list last week, "We plan to shorten the release cycle for Firefox desktop and Android from 4 weeks to 2 weeks from September 2026." He explained, "This is an experiment and does not mean we have to ship everything twice as fast. There is no need to rush work that is not ready, and features can still take as much time as needed."

He said, "The current goal is to release Firefox 155 on Sept. 1 rather than Sept. 15," and added, "We will closely review the results in practice and adjust if needed."

The change has already been reflected in the Firefox release calendar. Firefox 153 and 154 keep the existing four-week cycle, but from 155 it is moved up to Sept. 1 and is released at roughly two-week intervals thereafter.

Mozilla is attempting this for the first time in more than 10 years. Google also announced a similar change for Chrome in March.

Firefox 153 is scheduled for release on the 21st. Firefox 153 adds features to merge multiple PDFs into one by drag-and-drop in the PDF sidebar and to insert images into a PDF as a new page. It also improves PDF text highlighting.