Why We Built a Free Collaborative LaTeX Editor (an Overleaf Alternative That Doesn’t Paywall Teamwork)

If you’ve ever written a thesis or a research paper with a co-author, you already know the specific kind of pain this story starts with.

My co-founder and I were finishing our undergraduate thesis together. We wrote in LaTeX, like most people do for anything with equations, citations, and a page count that scares you. And we kept slamming into the same wall: real-time collaboration on the editor we were using was locked behind a paywall. So we did what everyone does — we emailed .tex files back and forth, pasted each other's edits in by hand, and occasionally overwrote a paragraph someone had spent an hour on.

At some point the absurdity of it landed. We were using one of the most powerful typesetting systems ever made, and the bottleneck wasn’t the math or the formatting — it was that two people couldn’t comfortably write in the same document at the same time without paying for the privilege.

So we built the thing we wished existed. It’s called LetX, and this is the story of why, and a few things we learned about LaTeX that I didn’t expect.

The problem with collaborative LaTeX

LaTeX is brilliant and ancient at the same time. It was built for a single author on a single machine, compiling locally. Everything about the default workflow assumes that.

Collaboration was bolted on later, mostly by web-based editors, and the dominant one solved a real problem: it put LaTeX in the browser so you didn’t have to install a multi-gigabyte TeX distribution just to write a paper. That was genuinely great. But somewhere along the way, the part that matters most for student teams — multiple people editing together in real time — became the thing you had to pay for.

For a funded lab, that’s a rounding error. For two students writing a thesis, or a study group, or a first-time researcher in a country where that subscription is real money, it’s a barrier. And it’s a strange barrier, because collaboration is exactly what makes the tool worth using in a team.

What we actually built

LetX is a collaborative LaTeX editor that runs entirely in your browser. The short version of what it does:

Real-time collaboration, free and unlimited. Multiple people edit the same project at once, with live cursors, and you can invite as many collaborators as you want without hitting a paywall. This is the whole reason it exists.

Fast compiles. It compiles to PDF in about a second in most cases, server-side, so there’s no local TeX install to manage.

The things you’d expect from a serious editor. Full version history so you can roll back, SyncTeX so you can click in the source and jump to that spot in the PDF, and ZIP import so you can bring in existing projects — including ones exported from Overleaf.

Templates that save you the first hour. Publisher-ready templates for IEEE, ACM, Springer, and Elsevier, plus academic CVs and résumés.

A privacy line we won’t cross. Your writing is never used to train any AI model. As the people doing the writing, that mattered to us, and it turns out it matters to a lot of researchers too.

The hard part: making “editing together” actually work

The engineering challenge that ate the most time wasn’t compilation — it was collaboration.

When two people type in the same document at the same moment, something has to decide how those edits combine without one person clobbering the other. The naive approaches break in frustrating ways: lost characters, cursors jumping around, the document quietly diverging between two browsers.

We built the real-time layer on CRDTs (conflict-free replicated data types), using Yjs. Without going too deep: CRDTs let multiple copies of a document accept edits independently and then merge them into the same final result, deterministically, without a central lock deciding whose turn it is. It’s the same class of algorithm behind the multiplayer experience in tools like Figma. For text editing with several people in one file, it’s the difference between “this feels solid” and “I don’t trust this with my thesis.”

That trust question turned out to be the real product. People who’ve been burned by collaborative tools before don’t care about your feature list — they care whether the document will still be intact tomorrow.

What surprised us about LaTeX users

Two things.

First, the friction isn’t always where you think. We assumed compile speed would be the headline. It matters — waiting on a slow compile breaks your flow — but for a lot of people the deeper pain was simply collaborating without fear. Speed gets you in the door; reliability is why people stay.

Second, privacy is becoming a real decision factor. A few years ago, “we don’t train AI on your text” would have been a footnote. Now it’s one of the first things researchers ask about, especially people working on unpublished results. The academic world is quietly recalibrating what it’s willing to hand over to a cloud tool.

Where things stand

LetX is being used by over a thousand students and researchers across more than 40 universities in 15+ countries — places like BRAC University, TU Munich, the University of Ottawa, and UPC Barcelona. Almost all of that came from word of mouth: one person in a lab brings the rest of the lab.

It’s free, it runs in your browser, and if you’ve got an existing project you can drop in the ZIP and keep working. If you write LaTeX with other people and you’ve ever lost a paragraph to a merge mistake, I’d genuinely like to know whether this solves it for you — and where it doesn’t.

You can try it at www.letx.app

If you’ve tried collaborative LaTeX before and it broke your trust, I’d love to hear what happened — that’s the kind of feedback that actually makes the tool better.