The word “sync” feels slightly retro, like syncing an iPod to your computer in the early 2000s, or the magic of Dropbox’s file sync circa 2010s. So it was with surprise and delight that I’ve noticed sync seems to be having a moment among web developers here in 2025.
For example: The Syncing Era of the Web, sync engines are the future
Feeling this energy, I was motivated to join the organizing team at Sync Conf happening in San Francisco this November. This is my writeup on why I think sync is trending, and more broadly why it’s an ideal foundation for the next generation of web apps.
What is sync?
My definition of a synced app is one where the client (that is, the software running on the user’s personal device) gets a full, canonical copy of the documents relevant to the session, but can also be shared with your other devices or other users. Some examples: Apple Notes, Obsidian, Linear.
All but one of these examples are built natively. But advances in browser storage have made synced web apps possible in recent years.
Furthermore, in the past you had to build your own sync engines from scratch. But now there are many off-the-shelf sync engines ready for use (Zero, Electric, Jazz, LiveStore, ...). That means more developers are discovering the joys of building on sync.
UX benefits
Sync makes it easier to offer these benefits for your users:
- Next-frame UIs. Linear has set a new bar for performance using their home-grown syncing engine. By collocating the data with the app (rather than on a remote server) you can guarantee a response to user actions by next screen paint, rather than waiting for a 100ms round trip or the sleight-of-hand of optimistic UI.
- Multiplayer by default. Figma showed the world what CRDTs can do, but not everyone can invest massive engineering resources to build out a multiplayer engine. Sync systems typically make it easy to implement live or asynchronous multi-user documents.
- Offline capability. This isn’t important to everyone, but for some apps it’s critical. Regardless it’s pretty nice to not have your app immediately stop working the moment someone steps into an elevator, a subway, or an airplane. See Notion’s recent release of offline support based on rich-text CRDTs.
The baseline of user expectation quality and craft keeps rising. Sync is a way to get there.
DX benefits
And as the developer, your experience is improved with:
- A simplified stack. Sync means reducing or entirely eliminating codepaths for client-side caching, optimistic UI updates, network error handling, and even a lot of boilerplate CRUD operations in your backend API. Your job as an app developer is to model your data and build your UI, and the sync engine takes care of the rest.
- Lower hosting bills. For indie app developers, this can be a big deal. More of the work is done on the user’s computer, less on your backend.
Put simply, sync is a lever to ship better software, faster.
AI-assisted coding, AI agents
Serendipitously to all of the above are the dual booms of LLM-assisted coding and people building agentic apps in 2025. Sync fits extraordinarily well with both of these trends.
On the LLM-assisted coding side, the simplified stack serves the same purpose for an AI context window as for a human. Less bandwidth spent on boilerplate APIs and caching layers, more spent on the application logic.
On building agents, Ink & Switch explored co-creation with AI via a sync system in early 2024. Agentic and sync are natural complements because local-first is multiplayer by default, and agents are another sort of “player” in addition to human collaborators. Having all changes be visible, diffable, and auditable by the human in charge of the document is a perfect fit.
Relationship to local first
I first really noticed the energy around sync at Local-First Conf this year.
Local first is a set of principles to give users ownership of their work. It’s a superset (or perhaps an overlapping venn diagram) of sync. I have deep conviction about local first as a long-term path for making computers better.
But I like that pragmatic people are pulling out the adjacent-possible pieces of local first to bring to synced apps. Cory House’s deeply-researched slides Work Now, Sync Later do an excellent job of capturing how the grand ideals of local first relate to the pragmatic near-term benefits of sync engines.
See you at Sync Conf
All of this adds up to a tremendous moment of opportunity for thinking about how we build the best possible software in 2025 and forward. So the timing of the conference is good.
I’m excited about the speaker lineup, but even more about discussing all of the above and more with everyone who comes. Maybe you?