Today we’re excited to share the official launch of Replay, a browser that records all of the context that developers and engineers need to fix bugs faster.

It has been years since I’ve written a line of code… but there are some pain points that I’ll never forget. Nothing that I programmed ever compiled perfectly the first time. And as much as I enjoy the reward of building something, I wish I had the patience for debugging code.

Despite being decades into coding, most developers still debug with “printf” statements, essentially adding code to generate specific output while the program is executing. The output generated can then be used to help diagnose issues within the program. The more “stuck” developers are in fixing bugs, the more printf statements they add in hopes to “see” the problem… and as you can imagine, it can get quite messy. 

Knowing this problem firsthand (even if not in my day-to-day work), I immediately fell in love with Replay’s time-travel debugger demo when I first met the team in July 2020. Replay captures everything you need for the perfect bug report, all in one link. 

Here’s how it works. Replay lets you record websites. You just press a record button, save it, share it with others, and you can watch the video and inspect it with familiar devtools. More specifically, Replay records the runtime inputs and internal non-determinism needed to be able to rerun the runtime and get the same behavior later. When you’re viewing a replay of a website, on the backend, Replay is running the same browser to make the recording. The browser thinks it is running in a normal environment, but it is really in a simulation.

The need for Replay is pretty obvious; every developer/engineer spends countless hours debugging their code. But now, when an engineer gets stuck, they can share a replay. When a test fails, a developer clicks a link to view the replay. When a question is asked on Stack Overflow, people comment directly in the replay. And so on!

The concept of recording runtimes is not new, but it is incredibly difficult to build. Previous attempts have been either too buggy or slow, making them hard to scale. And that leads us to why we’re so excited: the team! The technical mastermind behind Replay is Brian Hackett (CTO, co-founder) who has been thinking about and working on this concept for a long time… in fact, his PhD at Stanford 10+ years ago laid the foundation for Replay. Jason Laster (CEO, co-founder) is an experienced software engineer and champion of developer tools who, alongside Brian, has inspired world class talent to come together to bring time travel debugging to life / at scale.

So far, early users LOVE Replay. Sign up and try the Replay browser today, and/or try Replay for Chrome and Node in beta!

In addition, the team is excited to share that they have raised their pre-seed round led by us and our friends at IA Ventures, followed by their seed round, led by A16z with participation from some incredible angels and operators.

You can learn much more about the product, the company, its mission and values, what’s ahead, etc. on their blog post here. And of course, they are hiring!