FMRL serves a website straight from your open browser tab over WebRTC, with no host and no upload

Most websites sit on a server somebody is paying for. An FMRL site sits in your browser, and the server in the middle is only a phone book.

The tagline reads “Ephemeral websites, content, live-streams… etc, served from their owners’ browsers.” When someone visits, FMRL introduces their browser to the owner’s, and the pages travel directly between the two over WebRTC, the same plumbing video calls use. The FMRL server, in the site’s own words about its role, only keeps the directory.

The host page is plain about where your stuff lives. Claim a name and “your files stay in this browser. The FMRL server only records your name.” Upload files or folders, or start from a starter site, and the name works as an address. You can also keep a site out of the directory: unlisted sites “still work for anyone who has the address.”

The word ephemeral is doing real work. The page never says in so many words what a visitor sees when your tab closes. But if the files are in your browser and visitors load them from it, a closed tab is a closed shop. (Ephemeral is a nice word for “offline.”) To move a site to another browser, you import a backup .zip that includes a host token. To go home, you go offline on purpose.

Then the math the page does not hide. “Each viewer gets their own copy straight from this browser, roughly 1 to 2.5 Mbps each,” it says, so “your upload speed limits how many people can watch.” Your cable plan’s famously stingy upload side is the whole capacity plan. A hundred visitors at the top of that range wants 250 Mbps going up, and the average home connection has nothing like that.

There are live streams, too. Go live with a camera or a shared screen, and the directory marks your site live and links to a player page. To put the stream on your own page, you add one script, /_fmrl/live.js, and an <fmrl-live> tag where the video goes.

The odd one is the backend. Drop a _worker.js file in the site and it answers requests to /api/, “like a small web server running in this tab,” with a small key-value store, env.store, that keeps JSON in the browser. The page calls the feature new, saying “it may change, and it may have rough edges,” and each request gets 30 seconds. So you can run an API from the same tab where you left a spreadsheet and a music player open.

The fine print is the kind you want to read before sharing. Cookies are shared across FMRL sites, so the page says not to use them for sign-ins or private data. localStorage stays separate per site. Claiming a name means agreeing to the terms of use.

I would bet this idea sticks around as a way to share a thing for an afternoon, not as a way to host a business. A tab-served site is the web as a living-room conversation: you’re there, they’re there, everyone leaves. That fits demos, game jams, one-off streams and “look at this thing I made” pages, where renting a server for a week feels silly.

The weak spot is the one every peer-to-peer service hits: it works beautifully until the owner closes the lid. Some tinkerers will want a headless always-on tab on a spare machine, at which point you have invented a server again, only slower and with more steps. When the page was checked, the directory had no sites listed and invited visitors to add the first.

Somebody has to be that somebody.