A Go library for rendering colored terminal diffs with word-level emphasis.
go-delta produces human-readable, unified or side-by-side diffs with ANSI colors. Changed segments are highlighted at the word level so you can see exactly what changed within each line - not just that a line changed.
Inline:
Side-by-side:
go get github.com/amterp/go-delta
import gd "github.com/amterp/go-delta"
// Simple diff with defaults
output := gd.Diff(old, new)
// Customized diff
output := gd.DiffWith(old, new,
gd.WithLayout(gd.LayoutSideBySide),
gd.WithContextLines(5),
gd.WithWidth(120),
)Diff and DiffWith return an empty string when the inputs are identical.
| Option | Default | Description |
|---|---|---|
WithLayout(mode) |
LayoutInline | Layout mode (see below) |
WithContextLines(n) |
3 | Unchanged lines shown around each change |
WithColor(on) |
auto | Force color on/off (auto-detects TTY) |
WithWidth(cols) |
auto | Terminal width for side-by-side modes |
Color auto-detection respects NO_COLOR and FORCE_COLOR environment variables.
- LayoutInline (default) - removals and additions on separate lines. Always shows full content.
- LayoutSideBySide - old and new text in side-by-side panels. Lines that exceed terminal width are truncated.
- LayoutPreferSideBySide - uses side-by-side when content fits within the terminal width, falls back to inline otherwise.
// Always side-by-side
gd.DiffWith(old, new, gd.WithLayout(gd.LayoutSideBySide))
// Side-by-side when it fits, inline otherwise
gd.DiffWith(old, new, gd.WithLayout(gd.LayoutPreferSideBySide))- Word-level emphasis - changed words are highlighted within changed lines, not just the whole line
- Three layouts - inline, side-by-side, or auto-fallback
- ANSI-aware - correctly handles input that already contains ANSI escape codes
- Wide character support - CJK and other double-width characters are measured correctly
- Smart line pairing - modified lines are paired using a greedy forward-search algorithm (inspired by Delta)
- Hunk separators - groups of changes are separated with context, just like unified diffs
go-delta runs a three-stage pipeline:
- Myers diff - computes the minimal edit script between old and new
- Needleman-Wunsch alignment - aligns tokens within changed line pairs to find word-level differences
- Rendering - formats the output as inline or side-by-side with ANSI colors