Find the bytes.

The exact public Foundation API from the merged Swift implementation supplies the result. A companion Boyer–Moore implementation in the same Swift/Wasm module explains every jump.

Page search: a search field repeatedly looks for a small pattern inside a much larger buffer. This is the same shape of problem—without claiming Safari uses this exact API.

Bytes to search

Needle Options

AUTHORITATIVE RESULT · SWIFT/WASM Load the real Foundation runtime local release module · loaded on demand

Data UTF-8 bytes

Ready Press “Next comparison” to start.

0 bytes inspected 0 positions skipped — naïve comparisons

CURRENT KERNEL SHIFT Waiting for Swift

Bad character — Good substring —

ALIGNMENT TIMELINE

Load Swift/Wasm to generate the trace.

FOUNDATION TABLES Bad-character shifts

Generated by Swift for the current needle.

Good-substring shifts

Suffix lengths

Foundation supplies the displayed range. The trace and tables come from the same Boyer–Moore kernel merged in swift-foundation commit 55a4bb5, with snapshots added around its real table writes, comparisons, and cursor shifts. JavaScript only maps that data onto this interface.

Merged implementation ↗ WWDC26 Foundation segment ↗