Chunked uploading is a feature (should work in Firefox and Chrome) that splits an upload into 1MB chunks to ensure that a large file can be transferred reliably. With chunked uploading enabled you can upload up to 500MB files. See the experimental preference in the "Upload Wizard" section: https://commons.wikimedia.org/wiki/Special:Preferences#mw-prefsection-uploa… You need to use Upload Wizard in order to use this feature. This has required some significant changes to the way uploads are handled by the API to avoid timeouts, so it's likely to still be fragile. Do play with it, and in particular comment on these bugs if you have useful observations to share: https://bugzilla.wikimedia.org/show_bug.cgi?id=36587 https://bugzilla.wikimedia.org/show_bug.cgi?id=36599 All best, Erik -- Erik Möller VP of Engineering and Product Development, Wikimedia Foundation Support Free Knowledge: https://wikimediafoundation.org/wiki/Donate