swift-fast-markdown

High-performance SwiftUI markdown parser built on md4c, with streaming support and iOS 26 Liquid Glass rendering.

SWIFT / PARSINGDeveloper toolsOpen source · public

Swift
SwiftUI
md4c
Open source

GitHub card for swift-fast-markdown: a SwiftUI markdown parser with md4c, streaming and iOS 26 Liquid Glass.

Back to work

MN://swift-fast-markdown — System route

$ trace "swift-fast-markdown"

markdown bytes
md4c parse
zero-copy IR
SwiftUI render

The problem

Markdown rendering in a SwiftUI app becomes a performance problem the moment the text streams in from a model token by token.

The constraint

It has to stay consumable as a remote SwiftPM dependency, which rules out unsafe build flags and keeps bounds and overflow checks on untrusted input.

The approach

An md4c-based parser produces a zero-copy intermediate representation of byte ranges, SwiftUI views keep stable identity for cheap diffing, and an incremental parser handles streaming chunks.

The outcome

Measured on an M4 Pro over a hundred iterations: about 0.22 ms to parse 10 KB, about 3.3 ms to render it to an AttributedString, and about 9 microseconds per streaming append, with 114 tests including CommonMark compliance.

MN://WORK

More work

See all work