sharkdp/hexyl

> A colored command-line hex viewer — a read-only xxd/hexdump replacement tuned for reading, not patching.

GitHub repo · License: Apache-2.0 OR MIT

Overview

hexyl is a terminal hex viewer written in Rust by David Peter (sharkdp), first published in late 2018¹. Its single differentiating idea is color: every byte is classified into one of a handful of categories — NULL bytes, printable ASCII, ASCII whitespace, other ASCII control bytes, and non-ASCII (> 0x7F) — and each category gets its own color in both the hex panel and the character panel². The result is that structure in a binary (string tables, zero padding, high-bit data) is visible at a glance rather than something you decode byte by byte from a monochrome dump.

The defining tradeoff is that hexyl is a viewer, not an editor and not a scripting primitive. It has no in-place editing, no "reverse" mode to turn a dump back into bytes, and its default output carries Unicode box-drawing borders and ANSI color that are meant for a human terminal rather than for grep/diff. Where xxd doubles as a binary-patching tool (xxd then xxd -r) and od emits stable, parseable columns, hexyl deliberately optimizes for the one task of looking at bytes. It has never shipped a 1.0 and remains on a 0.x line, so it treats itself as a small, stable utility rather than a stabilized API.

Like the author's other tools (fd, bat, hyperfine), hexyl is a focused single-purpose CLI with opinionated defaults; the binary and crate are both named hexyl, and it is packaged in most mainstream distributions and package managers.

Getting Started

cargo install hexyl        # Rust 1.56+; crate and binary are both "hexyl"
brew install hexyl         # macOS
sudo apt install hexyl     # Debian/Ubuntu (19.10+), Fedora, Arch, etc.

# Dump a file
hexyl /bin/ls

# First 64 bytes only, skipping the first 32
hexyl --length 64 --skip 32 firmware.bin

# Read from stdin
head -c 128 /dev/urandom | hexyl

# Two-panel default, or force a single panel and 4-byte groups
hexyl --panels 1 --group-size 4 data.bin

# Show byte values in binary instead of hex, plain ASCII borders
hexyl --base binary --border ascii data.bin

Architecture / How It Works

hexyl streams bytes from a file or stdin and renders the classic three-region hex layout: a left offset column, the hex byte values in the middle (16 bytes per row, split into groups), and a character panel on the right. The middle values can be rendered in binary, octal, decimal, or hexadecimal via --base, and the row can be split across one or more panels (--panels) with a configurable byte --group-size².

The coloring is the core logic: each byte is mapped to a category, and the same category color is used for that byte in both the numeric and character panels, so your eye can correlate the two. Category colors are configurable through HEXYL_COLOR_* environment variables (HEXYL_COLOR_ASCII_PRINTABLE, HEXYL_COLOR_NULL, HEXYL_COLOR_NONASCII, HEXYL_COLOR_OFFSET, and others), accepting the eight standard terminal colors, their "bright" variants, or #rrggbb hex values². Coloring respects --color <auto|always|never>.

hexyl also collapses runs of identical rows — "squeezing" — replacing long stretches of repeated bytes (typically zero padding) with a single marker line so that a mostly-empty region does not scroll a screenful of identical output. This is on by default and disabled with --no-squeezing / -v.

Beyond the binary, hexyl publishes a library crate exposing its Printer so other Rust programs can produce the same colored dump programmatically rather than shelling out. The tool is thin: argument parsing plus the printer, with no plugin system, no config file, and no interactive mode.

Production Notes

• It is read-only. There is no editing and no reverse/patch mode. If you need

to modify bytes, hexyl is the wrong tool — use xxd -r, dd, or a real hex editor. hexyl shows you where to patch; something else does the patch.

• Default output is for humans, not pipelines. Borders and ANSI color make

hexyl | grep, hexyl | diff, and byte-offset arithmetic awkward. For scripting, stable machine-readable dumps, or diffing two binaries, od -A x -t x1z or xxd are the better sources; reach for hexyl at the interactive prompt, not inside a script.

• Squeezing hides data by design. Because identical rows are collapsed by

default, a naive hexyl file does not show every byte of a zero-padded region. When you need the literal full dump (e.g. verifying padding), pass -v / --no-squeezing.

• No implicit paging or length cap. Without --length, hexyl dumps the

entire input; on a multi-megabyte file this floods the terminal. Combine with --length/--skip to window into a file, or pipe into a pager.

• Windows needs an ANSI-capable terminal. Color depends on ANSI escape

support — Windows Terminal or ConHost v2 (Windows 10 1703+); older consoles show escape sequences or no color².

• Color config is environment-only. There is no config file; persistent

color choices must live in shell startup as HEXYL_COLOR_* exports, which is easy to forget across machines.

When to Use / When Not

Use when:

• You are interactively inspecting a binary and want byte categories (null,

printable, control, high-bit) visually separated.

• You want a quick, good-looking dump of a file or piped stream with sensible

offset/hex/ASCII columns and no configuration.

• You want binary/octal/decimal value display or multi-panel layouts without

memorizing od format strings.

Avoid when:

• You need to edit or patch bytes — use a hex editor or xxd -r.
• You need stable, parseable output for scripts, diffs, or byte-offset tooling —

od/xxd are more predictable.

• You are on a locked-down host where installing a Rust binary is not worth it and

xxd/od/hexdump are already present.

Alternatives

• vim/vim — xxd ships with Vim; use it when you also need to convert a dump back

into binary (xxd -r) or want a tool that is already installed nearly everywhere.

• coreutils/coreutils — od gives POSIX, script-stable octal/hex/character dumps;

use it when output has to be parsed or reproduced deterministically.

• WerWolv/ImHex — a full graphical hex editor and reverse-engineering suite; use it

for pattern languages, data inspection, and editing rather than terminal viewing.

• pixel/hexedit — a classic curses-based terminal hex editor; use it when you need

to change bytes in place from a TTY.

• sharkdp/bat — sibling tool for text files (syntax highlighting, paging); reach

for it when the input is source or logs, not raw binary.

History

References

1. ^ sharkdp/hexyl repository — "A command-line hex viewer," created 2018-11-05. https://github.com/sharkdp/hexyl
2. ^ hexyl README — byte categories, HEXYL_COLOR_* configuration, installation, Windows ANSI requirement, dual MIT/Apache license. https://github.com/sharkdp/hexyl/blob/master/README.md
3. ^ hexyl releases and changelog. https://github.com/sharkdp/hexyl/releases

Tags

rust, cli, command-line, hex-viewer, hexdump, binary-data, hexadecimal, developer-tools, terminal, unix, reverse-engineering