July 28, 2026
Build speed or build beef?
Zig's Incremental Compilation Internals
Zig promises near-instant rebuilds, and the comments instantly turned into a speed war
TLDR: Zig says it can rebuild app changes in milliseconds by updating only the parts that changed, which could make coding feel dramatically faster. Commenters loved the speed boost, but quickly split into camps over missing details, design choices, and whether great tools can outweigh bigger language concerns.
Zig just dropped a big flex: its compiler can now rebuild changed parts of an app in 50–70 milliseconds after the first build, which is the kind of number that makes programmers stare at the screen like they’ve seen magic. The post itself is a deep dive into how Zig spots what changed, rebuilds only that slice, and patches the app directly instead of rebuilding everything from scratch. In normal-person terms: tweak a line, hit build, and it’s back almost immediately. Cue the community doing what it does best — applauding, nitpicking, and starting side quests in the comments.
The loudest cheer came from people who are frankly offended that software builds have been slow for this long. One commenter basically declared the whole industry asleep at the wheel, praising Zig for finally treating build speed like it matters. Another gave Zig’s behind-the-scenes tools a glowing review while still delivering a sharp little jab: great engineering, sure, but memory safety is still “table stakes,” so don’t expect a full love letter. And then, of course, came the practical crowd: does this work in release builds, or just the comfy developer mode? What about C code too? The skeptics also showed up with architecture critiques, asking why Zig builds one huge debug app instead of lots of tiny pieces. Translation: even when the demo is fast, the internet still wants to redesign the engine. The vibe is equal parts hype, side-eye, and nerd fight, which is exactly how you know people think this matters.
Key Points
- •The article says Zig’s incremental compilation can detect changed functions and declarations, recompile only those parts, and patch the output binary directly.
- •According to the article, the feature has matured from a proof of concept to a workflow used daily by most of the Zig core team on real-world projects.
- •In the Fizzy demo, the initial build takes about 5 seconds and subsequent rebuilds after edits complete in roughly 50–70 milliseconds.
- •The demo used Zig’s master branch because Zig 0.16.0 lacks some linker features needed for the showcased experience; tagged-release users may need to wait for 0.17.0.
- •The article explains that Zig’s file-level pipeline—reading source files, parsing to AST, converting to ZIR with AstGen, and caching per-file outputs—supports both parallel execution and incremental rebuilds.