salti

salti is a terminal based multiple sequence alignment (MSA) viewer for FASTA files. It is designed for fast interactive browsing primarily on remote servers, and HPC environments, or anytime you dont want to leave the terminal.

Features

https://github.com/user-attachments/assets/2592a9ac-43ba-42bc-8a29-e4d1d42d904a

Fast

salti is built for fast browsing and loading of large alignments, using tokio for async processing. This is in part achieved by:

• Background threads handle tasks such as consensus/conservation calculation and file loading, allowing these to complete dynamically without blocking the UI.
• Rendering only the visible portion of the alignment, updating the view on state changes rather than every frame tick, and caching consensus and conservation calculations in a window around the currently visible region.

It can handle alignments with thousands of sequences and >200,000 positions without lag (tested with ~3k mpox alignments on Ghostty and Kitty, which both support GPU acceleration, the performance may vary on other terminals).

Load files over HTTP/HTTPS/SSH

Thanks to the cool Paraseq library salti can transparently load over HTTP/HTTPS and SSH, in addition to local files. Just provide the URL or SSH path to the load command, e.g. :load https://example.com/alignment.fasta or :load ssh://user@host/path/to/alignment.fasta.

Themes

salti supports multiple colour themes, which can be switched with the set-theme command. Available themes so far are:

• everforest-dark - the default theme, based on the everforest colorscheme.
• solarized-light - a light theme based on the solarized palette.
• tokyo-night - a dark theme based on the tokyo night palette.
• terminal-default - uses terminal-provided ANSI colours and defaults.

Command palette

Press : to open a command palette for most actions. See Usage for details.

Nucleotide and Amino acid support

salti automatically detects whether your alignment is nucleotide (NT) or amino acid (AA), then applies the correct rendering mode.

Translation

Can translate NT codons to AA on the fly, with support for all 3 frames, although designed for browsing, rather than a dedicated translation tool.

Useful viz tools

• Collapse positions that match the reference or consensus to . for easier visualisation of differences.
• Mouse selection to highlight regions or sequences
• Pin important sequences fixed at the top while browsing.

Installation

Binaries:

Precompiled binaries for Linux, MacOS and Windows are attached to the latest release.

Cargo:

Requires cargo

cargo install salti

Build from source:

Install rust toolchain:

To install please refer to the rust documentation: docs

Clone the repository:

git clone https://github.com/Sam-Sims/salti

Build and add to path:

cd salti
cargo build --release
export PATH=$PATH:$(pwd)/target/release

All executables will be in the directory salti/target/release.

Usage

Tested on my setup (Arch linux + ghostty) - but should work on any modern terminal.

salti <alignment.fasta>

If no file is passed, the app starts and waits for you to load one via the command palette.

Quick start keybinds

I plan to add a help screen in the future for reference in app, but for now here are the most useful keybindings:

Global keybindings

• q - Quit.
• : - Opens the command palette.
• Up / Down - Scroll vertically
• Left / Right - Scroll horizontally.
• Shift + A navigation key scrolls faster in that direction.
• Alt+Left / Alt+Right - Scroll sequence name pane.
• Left cick - Select a sequence or position. Click again to clear selection.
• Ctrl + Left click - Select a range of sequences or positions

Command palette

Most features can be accessed through the command palette (this is heavily inspired by the helix editors implementation!).

Open with :, then type a command.

• Enter confirms selection.
• Tab / Shift+Tab cycles any candidates.
• Esc closes the palette.

Commands:

• jump-position - Jump to a 1-based alignment position.
• jump-sequence - Jump to a sequence by name
• pin-sequence - Pin a visible sequence to the top of the alignment view.
• unpin-sequence - Remove a sequence from the pinned group.
• set-filter - Filter visible sequences by regex.
• clear-filter - Clear the active filter.
• set-reference - Set a reference sequence .
• toggle-translate - Toggle AA translation.
• set-diff-mode - Set diff rendering mode (off, reference, or consensus).
• load-alignment (alias: load) - Load an alignment file.
• set-consensus-method - Choose majority or majority-non-gap.
• set-translation-frame - Set translation frame (1, 2, or 3).
• set-theme - Set active theme (everforest-dark, solarized-light, tokyo-night, or terminal-default).
• set-sequence-type - Override auto-detection if it fails (dna or aa).
• quit - Quit the app.

Some notes on features

Fuzzy matching

All commands that take string input support fuzzy matching. For example, jump-sequence will match any sequence name that contains the input string. If multiple candidates match, you can cycle through them with Tab / Shift+Tab.

Consensus method

Two methods are available for consensus calculation:

• majority - The most common character at each position, including gaps.
• majority-non-gap - The most common character at each position, excluding gaps

If there is a tie for most common character, one is chosen at random.

Consensus is calculated in the background

Pinned behaviour

• Pinned sequences stay visible and remain at the top, even when they do not match the active filter.
• Setting a sequence as reference removes it from pinned state and hides it as the reference row.

Data/Rendering

• Input must be FASTA with equal sequence lengths across records.
• Sequence type is auto-detected on load; you can override it if its wrong.
  • It tries to work this out by picking 100 random alignments and checking if over 50% of characters are valid amino acid characters. If so, it assumes its an AA alignment, otherwise NT.