lazycsv

A blazingly fast terminal UI for CSV files. Open a 10GB file instantly. Query it with SQL. Convert between any format. Edit cells with a full vim editor inside. All from your terminal, zero config needed.

Inspired by lazygit, lazydocker, and lazysql.

Why LazyCSV?

• Billions of rows, instant open - memory-mapped lazy loading. No loading screen, no waiting. Scroll through files larger than RAM like they're empty
• SQL on CSV - :sql opens a full query editor backed by DuckDB. JOIN across files, aggregate, filter, INSERT, UPDATE, DELETE — your data, your queries
• Edit like vim - insert mode for quick fixes, magnifier mode for a full vim editor inside any cell. Macros, visual mode, undo/redo. It's vim, in your data
• Your keys, your way - ships with vim, emacs, and excel presets. Customize every binding to match your workflow
• File explorer - browse all CSVs in a directory with a 3-column file picker. Switch files like Excel sheets, no cd required
• Multi-format powerhouse - open CSV, TSV, XLSX, ODS, JSON, Parquet. Export to any of them. Convert from the CLI: lazycsv data.xlsx -o out.json
• CLI superpowers - sort, dedup, generate synthetic data, query non-interactively, grab stats — all without opening the TUI
• Highly configurable, great defaults - works out of the box. 11 theme presets (Gruvbox, Dracula, Nord, Catppuccin, Tokyo Night...), 3 keybinding presets, and deep config when you want control. If you don't — it just works

Features

Performance

• Lazy loading - files under 10MB load into memory for instant access. Larger files use memory-mapped I/O with an LRU row cache, so you can open files bigger than your RAM
• 60 FPS rendering - virtual scrolling only draws visible cells (O(1) per frame). Files with 100K+ rows render at 2500+ FPS
• Parallel search - regex search across 100K rows in ~20ms using rayon multi-core
• DuckDB-backed queries - SELECT on 100K rows in under 50ms, JOINs in under 200ms

SQL Query Mode

Open a full SQL editor inside the TUI with :sql:

• Full DuckDB SQL - SELECT, WHERE, ORDER BY, GROUP BY, HAVING, JOINs, aggregates, string functions, math operators
• DML support - INSERT, UPDATE, DELETE, ALTER, DROP, CREATE
• Multi-file JOINs - all supported files in the same directory are auto-loaded as tables
• SQL IntelliSense - context-aware auto-completion for table names, column names, and SQL keywords
• Fuzzy error suggestions - mistyped column name? Levenshtein distance suggests the right one
• Query history - persisted to ~/.config/lazycsv/sql_history, browse with Up/Down
• Cancellable - hit Esc to kill long-running queries
• Results as virtual table - query output appears as a new tab in the file switcher

Editing

Insert mode (i, a, s) - quick single-line cell editing for fixes and updates:

• Tab saves and moves right, Enter saves and moves down, Esc cancels
• Ctrl+w deletes word, Ctrl+u deletes to start, Ctrl+h backspaces

Magnifier mode (Enter) - a full vim editor embedded inside any cell:

• All vim motions: hjkl, w/b/e, 0/$, gg/G, f/F/t/T
• All vim operators: d, c, y, p, r, x, J, >>/<<
• Visual mode, search (/, n, N), undo/redo (u, Ctrl+r)
• Alt+hjkl to navigate to adjacent cells without closing
• Perfect for JSON, multi-line text, or any cell that needs real editing power

Row and column operations:

• dd delete row, yy yank row, p/P paste row, 5dd delete 5 rows
• ,dd delete column, ,yy yank column, ,p/,P paste column
• o/O insert row below/above, ,o/,O insert column right/left
• cc clear row, gj/gk swap rows, drag with mouse to reorder

Cell transforms:

• ~ toggle case, gU uppercase, gu lowercase, g~ title case
• g. toggle boolean values (yes/no, true/false, 1/0, on/off)
• s/old/new/g find and replace — in a cell, a range, or across all data

Visual Mode

• v cell-by-cell selection, V row selection, ,v column selection
• d delete, y yank, c change, p paste
• o toggle selection corner, gv re-select last visual range
• gs show statistics for selected cells

Search

• / opens regex search with live results as you type
• n/N next/previous match, * search for current cell value
• Match counter shows [current/total] in status bar
• Case-insensitive by default with automatic regex fallback

Undo, Redo, and Macros

• u undo, Ctrl+r redo — up to 1000 steps, configurable
• . repeats the last edit operation
• qa...q records a macro into register a-z, @a replays, @@ repeats last
• Per-file undo history preserved across file switches

File Explorer

:files opens a yazi-inspired 3-column file browser:

• Parent | Current | Preview layout
• Type to filter, j/k to navigate, Enter to open
• File operations: rename (r), delete (d), copy (y), move (m), new file (n)
• : opens a shell prompt with $CWD, $FILE, $NAME, $EXT variable substitution
• Navigate directories, spot-preview files before opening
• Quick switching between files with [ and ]

Multi-Format Support

Read: CSV, TSV, CSV.GZ, TSV.GZ, XLSX, XLS, ODS, JSON, NDJSON/JSONL, Parquet, SQLite

Write/Export: CSV, TSV, JSON, Markdown, XLSX, ODS, Parquet

From the TUI: :export json or :export data.xlsx

From the CLI: lazycsv data.xlsx -o out.json, lazycsv data.csv -o out.parquet

Pipe support: cat data.csv | lazycsv or lazycsv -q "SELECT * FROM stdin"

CLI Superpowers

Everything the TUI can do, you can do from the command line:

# SQL query non-interactively
lazycsv data.csv -q "SELECT * FROM data WHERE amount > 100"

# Sort by column
lazycsv data.csv --sort Name

# Print stats (type, min, max, mean, stddev, median, mode, cardinality)
lazycsv data.csv --stats

# Print headers, row count, or column count
lazycsv data.csv --headers
lazycsv data.csv --rows
lazycsv data.csv --columns

# Deduplicate with primary key support
lazycsv data.csv --dedup --keep-first

# Split a large file into smaller ones
lazycsv data.csv --split 10000

# Generate realistic synthetic data
lazycsv --generate customer --rows 10000 -o customers.csv

# Convert formats
lazycsv spreadsheet.xlsx -o data.json
lazycsv data.csv -o out.parquet

# Extract Excel sheets
lazycsv spreadsheet.xlsx -x

# Add headers to a headerless file
lazycsv data.csv --add-header "Name,Age,City"

# Clipboard integration
lazycsv data.csv -C          # copy output to clipboard
lazycsv -P                    # paste from clipboard into lazycsv

# Locale-aware number formatting
lazycsv data.csv --format

Formulas

Excel-compatible formula engine for spreadsheet power users:

• Aggregates: =SUM(A1:A5), =AVERAGE(A1:A5), =MIN(...), =MAX(...), =COUNT(...)
• Math: =POWER(), =CEILING(), =FLOOR()
• Text: =CONCAT(), =TRIM(), =UPPER(), =LOWER(), =PROPER(), =LEFT(), =RIGHT(), =MID(), =SUBSTITUTE()
• Logic: =IF(condition, true_val, false_val) with comparison operators
• Lookup: =VLOOKUP(), =HLOOKUP()
• Date: =NOW(), =TODAY(), =DATEDIF()
• Formula bar displays the formula when cursor is on a formula cell
• Auto-completion popup for function names and cell references
• Imports formulas from XLSX spreadsheets

Conditional Formatting

Color columns based on conditions:

:bgcolor Amount red ">1000"       # red background where Amount > 1000
:bgcolor Status green "=active"    # green where Status equals "active"
:fgcolor Name blue "~^admin"      # blue text where Name matches regex
:bgcolor # green "and(>0,<=100)"   # compound conditions
:clearview                         # remove all custom colors

Colors persist across sessions in ~/.config/lazycsv/views.json.

Sort, Stats, and Substitute

• :sort Name sort ascending by column, :sort! Name descending, multi-column: :sort Dept,Name
• :stats show column statistics overlay (count, sum, avg, min, max, distinct), :stats A for one column
• :sum, :avg, :count, :distinct for quick single-stat lookups
• s/old/new/ replace in current cell, %s/old/new/g replace everywhere, 5,10s/old/new/g in a row range, B,Ds/old/new/g in a column range

Session and Persistence

• :w save, :W save all, :wq save and quit, :q! force quit
• Dirty file indicator (* after filename)
• External modification detection — polls every 2 seconds, prompts to reload
• View state (column widths, types, colors, frozen columns) saved per file across sessions
• :freeze A,B pin columns, :freeze 1,3 pin rows, :unfreeze to remove
• :type A number annotate column types for proper formatting

Configuration

Default config location: ~/.config/lazycsv/config.toml
Per-directory overrides: .lazycsv.toml in any directory

[defaults]
delimiter = ","
encoding = "utf-8"
zebra_striping = true
max_column_width = 50
undo_limit = 1000

# Full theme customization with 11 presets
[ui]
bg = "#282c34"
fg = "#abb2bf"

# Every keybinding remappable, 199 named actions
# Three presets: vim (default), emacs, excel

Hot-reload — save your config and changes apply instantly. No restart needed.

11 built-in themes: Gruvbox (dark/light), Dracula, Nord, Catppuccin (Mocha/Macchiato/Frappe/Latte), Solarized (dark/light), Tokyo Night

3 keybinding presets: inherit = "vim" (default), inherit = "emacs", inherit = "excel", or inherit = "none" for a blank slate. Every key in every mode is remappable.

Mouse Support

• Click to select cells, click headers to select columns, click row gutters to select rows
• Double-click enters insert mode
• Right-click context menu (cut, copy, paste, clear, insert, delete)
• Drag column headers to reorder columns
• Drag row gutters to reorder rows
• Mouse wheel for scrolling

Install

Pre-built binaries (recommended)

Download the latest release for your platform from GitHub Releases.

macOS (Apple Silicon)

curl -L https://github.com/funkybooboo/lazycsv/releases/latest/download/lazycsv-v0.24.4-aarch64-apple-darwin.tar.gz | tar xz
sudo mv lazycsv /usr/local/bin/

macOS (Intel)

curl -L https://github.com/funkybooboo/lazycsv/releases/latest/download/lazycsv-v0.24.4-x86_64-apple-darwin.tar.gz | tar xz
sudo mv lazycsv /usr/local/bin/

Linux (x86_64)

curl -L https://github.com/funkybooboo/lazycsv/releases/latest/download/lazycsv-v0.24.4-x86_64-unknown-linux-gnu.tar.gz | tar xz
sudo mv lazycsv /usr/local/bin/

Windows

Download lazycsv-v0.24.4-x86_64-pc-windows-msvc.zip from the releases page, extract, and add to your PATH.

Build from source

Requires the Rust toolchain. Install it first if you don't have it:

macOS

brew install rust

or

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Linux (Debian/Ubuntu)

sudo apt install cargo

or for the latest Rust version:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Windows

Download and run rustup-init.exe from the official site.

Then build lazycsv:

git clone https://github.com/funkybooboo/lazycsv.git
cd lazycsv
cargo install --path .

Quick Start

# Open current directory (scans for CSV files)
lazycsv

# Open specific file
lazycsv data.csv

# Open a directory
lazycsv ./data/

# With options
lazycsv data.csv --delimiter ';' --no-headers

# Non-interactive query mode
lazycsv data.csv --query "SELECT * FROM data WHERE amount > 100"

# Locale-aware number formatting
lazycsv data.csv --format

Essential Keys

Key	Action
hjkl or arrows	Move around (with count: 5j, 10h)
gg / G	Jump to first / last row
5G / :5	Jump to row 5
:B / :A5	Jump to column B or cell A5
w / b / e	Next/prev/last non-empty cell
i / a / s	Quick edit cell (Insert mode)
Enter	Magnifier — full vim editor inside the cell
o / O	Insert row below/above
dd / yy / p	Delete/yank/paste row
,dd / ,yy / ,p	Delete/yank/paste column
v / V / ,v	Visual select (cell/row/column)
/	Search (regex, live results)
n / N	Next/previous match
u / Ctrl+r	Undo / Redo
.	Repeat last edit
~ / gU / gu / g~	Toggle/upper/lower/title case
g.	Toggle boolean (yes/no, true/false)
gj / gk	Swap row down/up
:sql	SQL query mode (DuckDB-backed)
:sort / :sort!	Sort ascending/descending
:stats	Column statistics overlay
:files	File explorer (browse, open, manage files)
:export	Export to JSON, TSV, Markdown, XLSX, ODS, Parquet
s/old/new/g	Find and replace in cells
qa...q / @a	Record / replay macro (26 registers)
Esc	Cancel loading/queries
zt / zz / zb	Scroll row to top/center/bottom
?	Show help
:w / :q	Save / Quit

Press ? in the app for the full keybinding reference.

Documentation

• Keybindings - Every keyboard shortcut by version
• Design - How it looks and feels
• Architecture - How it works
• Development - How to contribute

Development

# Using mise (recommended)
mise run run        # run with sample.csv
mise run test       # run tests
mise run ci         # format, lint, test

# Or with Cargo
cargo run -- sample.csv
cargo test

See docs/development.md for contributing guidelines.

Philosophy

LazyCSV follows the "lazy tools" design:

1. Keyboard first - mouse optional, every action has a key
2. Fast - instant response, lazy-loaded for infinite scale
3. Simple - no configuration required, sensible defaults
4. Powerful - vim-style efficiency, SQL queries, format conversion
5. Vim-first - if it works in vim, it should work here

License

MIT License - see LICENSE file for details.

Credits

Built with:

• ratatui - TUI framework
• DuckDB - SQL query engine
• csv - CSV parsing by BurntSushi
• Rust

Inspired by the excellent "lazy" tools: lazygit | lazydocker | lazysql | lazyssh

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Have fun exploring your data!