WebTorrent is one of the most novel uses of some modern browser technologies that I have recently learned about. Using WebRTC is able to implement a truly peer-to-peer data transport on top of support offered by existing browsers. I came across WebTorrent when I was doing some research on what potential future options might exist for more scalable distribution of free and open source libraries and applications. In this post, I want to share some thoughts and observations I jotted down while considering WebTorrent.

WebTorrent basically implements BitTorrent on top of the browser technology stack, which means that as clients download a file they also help upload it to other clients. Before the popularization of cloud providers, streaming services, and self-service CDN companies, the BitTorrent model was pretty much the only viable mechanism for many large free and open source projects to distribute larger binaries. Not counting those who had friends with fast .edu or Internet2 uplinks who started to offer hosting and distribution like my pals at the Oregon State University Open Source Lab. BitTorrent’s popularity seems to have largely faded when most of the interesting videos, and a lot of porn, started to become available via far simpler streaming services like YouTube, etc.

To date the number one inhibitor of BitTorrent conceptually is that it has never been natively integrated to the browser. The internet is much more than just www and what we see in the browser, but for most mainstream consumers if it is not available over the web, it might as well not exist.

WebTorrent solves that key and crucial limitation which on its own is quite an impressive achievement. It does however come with some key drawbacks that have given me pause on rushing to roll out WebTorrent in the projects with which I am affiliated:

  1. WebTorrent effectively operates outside of the existing BitTorrent network. Since it is over WebRTC there are limitations on creating connections to other native BitTorrent clients and trackers which operate over TCP or UDP. For a file provider, such as an open source project, would need to operate two “seeders” should they wish to serve a file over both BitTorrent and WebTorrent.
  2. Browser-based implementations of WebTorrent, such as that found in PeerTube run into a classic BitTorrent problem: insufficient seeders. PeerTube is a decentralized video streaming platform which has support for federation and video redundancy. When clients are viewing a video or stream, their browser window sets up a WebTorrent session and they begin downloading from existing seeders, typically the PeerTube instance the user typed into their address bar. If they’re lucky, the PeerTube instance has been “followed” and another PeerTube instance has provided “video redundancy” meaning there may possibly be more than one seeder for the WebTorrent client. Additionally the person watching the video becomes a seeder as well.

    In practice what this means is that WebTorrent can only help avoid massive bandwidth requirements for the originating PeerTube instance if:

    • There are multiple PeerTube instances providing video redundancy on the video being watched.
    • Multiple viewers are watching the video simultaneously.

    Generally speaking, once a viewer closes the browser window/tab, they stop seeding the file. This means that practically WebTorrent-based applications may only be advantageous if they can convince users to keep their browsers seeding after they have finished with the file.

  3. Server-side support for WebTorrent is not quite as mature as I would have hoped. There are relatively stable Node packages such as webtorrent-hybrid which can help systems administrator run WebTorrent seeders without needing a browser. Outside of the Node ecosystem, the only implementation I could find of any notoriety was the recently added support for WebTorrent in the libtorrent C++ library. I have no opinions on the library itself, but the nature of many C++ libraries like libtorrent makes them somewhat challenging to interoperate with in languages that provide fast-function interfaces (FFI) such as Python and Ruby, or those which provide native C-interop such as Java, Golang, and Rust.

WebTorrent is still so cool. I am really hoping to it continues to grow and succeed. With some very compelling implementations in PeerTube and Instant.io, I think WebTorrent has the potential to provide a really liberating foundation for decentralizing some facets of our internet infrastructure.

It might not yet be what I want it to be, but it’s definitely something worth keeping an eye on!