A single-file, local-first, multi-sheet spreadsheet.

No accounts. No cloud. No subscription. No analytics. No tracking. One HTML file.

MIT licensed. Your data stays in a plain JSON file on your disk.

Part of the LocalOffice suite, alongside DeckBuilder and Context Protocol.

The local AI reading the budget and flagging every over-budget row, applied as one undoable patch:

Change one gain on the Joints sheet and the Computed sheet recomputes damping ratio, settling time, and class live. Here, J2 tunes from underdamped to critically damped:

Why LocalSheets feels different

Most spreadsheet tools want your data on their servers, your access behind their login, your money in their subscription, and your workflow locked into their format.

LocalSheets assumes the opposite: software disappears, but files persist.

• No cloud. No accounts. No telemetry. The app is a single HTML file you open from disk.
• No vendor format. Workbooks are plain JSON: git diff works on them, you can edit one in a text editor, and the schema is short enough to read in five minutes.
• No dependencies. Zero npm packages, zero CDN calls, zero embedded fonts. The whole product is one ~260 KB file; mirror it, fork it, archive it, run it on an air-gapped laptop in 2046.
• MIT. Use it, modify it, ship it inside your own product. No callbacks home.

Provable zero-leak

The repo contains a network-surface audit you can re-run. Every potential outbound channel in localsheets.html:

The AI panel is the only outbound call. Don't click it (or don't run Ollama) and the app is fully airgapped.

Verify it yourself (60 seconds)

Don't take this on faith. Run these two commands against the file you downloaded:

# 1. Network surface: should print exactly 2 lines, both fetches to localhost:11434
grep -nE 'fetch\(|XMLHttpRequest|WebSocket|sendBeacon' localsheets.html   # Linux / macOS / Git Bash
Select-String -Path .\localsheets.html -Pattern "fetch\(", "XMLHttpRequest", "WebSocket", "sendBeacon"  # Windows PowerShell

Expected output (line numbers will match the version you downloaded):

5494:      const res = await fetch(this.host + '/api/tags', { method: 'GET' });
5594:      const res = await fetch(this.host + '/api/generate', {

this.host is a hard-coded const 'http://localhost:11434' (see const AI = { near the top of the AI section). There is no let, no DOM input, no env var that can override it.

# 2. Integrity: confirm the file you have is the file the maintainer audited
sha256sum localsheets.html      # Linux / Git Bash on Windows
shasum -a 256 localsheets.html  # macOS

Compare with the SHA-256 published on the GitHub Releases page for the version you downloaded. If they match, the file you have is the file that was audited. If they don't, don't run it.

This is the design that lets the same workbook hold a household budget and a 6-DOF robot-arm PID calibration, because the engine is just files and formulas.

Features in v1.1

New in v1.1

• Charts: Data ▾ → Chart selection… renders a bar / line / pie SVG of the selected range, with copy + download
• =SPARKLINE(range, [type], [color]): inline SVG line or bar chart inside a single cell
• Absolute references: $A$1, $A1, A$1 are tokenized and honored by the fill handle
• Insert / delete row or column auto-rewrites formula text: including cross-sheet refs. Refs to a deleted row become #REF!; refs past it shift up. Same for columns.
• Fill-handle propagates formulas: dragging =A1+B1 down one row produces =A2+B2 instead of copying the value
• Local AI panel (toolbar AI): talks to a local Ollama instance, with two modes: freeform text reply or structured JSON-patch mutations
• JSONL / NDJSON import: drop a .jsonl or .log file (one JSON object per line, common in robotics/telemetry/log streaming) into Import CSV / JSONL. The union of keys becomes the header row; one row per line. Auto-detects by content, so .txt files containing JSONL also work.
• 10,000-row sheets (up from 1,000)
• Browser e2e suite: 28 Playwright specs across 6 files run headlessly on Chromium and WebKit (see e2e/STATUS.md)

Workbook

• Multi-sheet workbooks: up to 100 sheets per file, each up to 10,000 rows × 702 columns (A–ZZ)
• Tab bar at the bottom: click to switch, double-click to rename, right-click to duplicate/delete/reorder
• Save / load as .localsheet.json (schema v2.0); v1.0 files auto-migrate on open
• File System Access API in Chrome/Edge: real in-place save; download fallback elsewhere

Formula & Equations

• 99 functions across math, stats, text, lookup, dates, financial, info
• Multi-sheet references: =Sheet2!A1, =SUM('My Data'!A1:B10)
• Cycle detection (#CIRC!), proper error tokens (#DIV/0!, #VALUE!, #REF!, #NAME?, #PARSE!, #N/A, #NUM!)
• Dependency graph with topological recalc: change a cell and all dependents update

Editing

• Range selection: click+drag, Shift+click, Shift+arrows
• Whole row / column / sheet selection: click a row number, column letter, or the top-left corner to select all of it
• Jump to any cell: click the address box (top-left) or press Ctrl+G and type a cell like ZZ500 or Sheet2!AA10
• Auto-extend: scroll near the right or bottom edge and the grid expands in chunks (26 cols / 50 rows) all the way to ZZ × row 10000
• Formula reference picking: while editing a formula, click or drag any cell to insert its reference (A1 or A1:A10) at the cursor; picked range shows a dashed accent outline
• Auto-pair parentheses: typing ( in a formula inserts () with the cursor between; ) skips over a matching close; Backspace deletes the pair
• Multi-cell copy/paste as TSV (round-trips with Excel and Google Sheets)
• Undo / Redo up to 100 actions (Ctrl+Z / Ctrl+Y or Ctrl+Shift+Z) including bulk ops (paste, clear, format, sort, replace-all)
• Insert/delete/sort rows and columns via toolbar dropdown or right-click
• Column and row resize by dragging the right edge of a column header or bottom edge of a row header
• Freeze panes: top row / first column / both / freeze at selection / unfreeze
• Sort columns A→Z or Z→A from the right-click menu or Data ▾ toolbar dropdown (sorts the populated range, preserves row groups)
• Sort range with / without header: select cells, then Data → Sort range with header…; treats the first row as a label and keeps it in place while sorting the rest
• Format painter: pick the format of the active cell, then click anywhere to paint it

Formatting

• Bold / Italic / Underline / Strikethrough per cell (Ctrl+B / Ctrl+I / Ctrl+U + S button)
• Wrap text: toggle word-wrap; row auto-grows to fit
• Font size: 9 through 32 pt, rows auto-grow for larger text
• Text alignment: Left, Center, Right
• Number formats: General, Number (1,234.56), Currency ($1,234.56), Percent (42%), Integer (1,235), Date (2026-05-24), Date US (05/24/2026)
• Fill color: 11-swatch palette plus a custom color picker; applies to empty cells too
• Text color: same palette mechanic for foreground
• Borders: All / Outside-only / Top / Bottom / Left / Right / None (medium-gray, visible in both themes)
• Conditional formatting: per-sheet rules (> 0 → green, < 0 → red, etc.) applied at render time

Data

• Data validation lists: right-click → Set list values… gives the cell a dropdown of allowed values; a small ▾ arrow on the cell opens the picker
• Cell notes: right-click → Add / edit note; a red triangle in the corner marks notes; hover to read
• Named ranges: toolbar Names… dialog (e.g. Revenue = Sheet1!B2:B13); names work inside formulas: =SUM(Revenue)
• Tables / Lists (Excel-style "Format as Table"): Ctrl+L or Ctrl+T (or Data → Format selection as table, or right-click → Create list / table). If you have a range selected it uses that; if you're on a single cell inside data, it auto-detects the contiguous range like Excel does. The first row becomes a styled header (accent background, white text) with a ▾ filter chip on each column. Body rows get zebra stripes. To convert back to a plain range, use Remove table from the same menus.
• Fill handle: select one or more cells, then drag the small accent square at the bottom-right corner down or right. If the source values are an arithmetic series (1, 2, 3 or 10, 20, 30), it continues the pattern; otherwise it repeats the source values in cycle.
• Merge cells: select a range and pick Merge cells (right-click or Data ▾). Cells visually combine into one block; only the top-left value is kept. Unmerge on the merged cell restores it.

UX

• Find / Replace / Find All (Ctrl+F): current sheet or all sheets, optional case-sensitive; Enter advances; Find All highlights every match in yellow and shows a clickable results list at the bottom of the panel (click a result to jump to that cell; the current one is highlighted in orange)
• Column filter: right-click → Filter column… shows a checklist of unique values; uncheck to hide rows. No header row required. Multiple columns can be filtered at once; filtered columns get a ▾ chip on the header.
• Theme toggle: Light / Dark / Auto, remembered across sessions
• Range summary in the status bar: count, sum, average for the active selection
• Right-click context menu: copy, paste, insert/delete row+col without leaving the grid
• Help overlay (?): full keyboard reference and function list
• Unsaved changes dot in the toolbar, browser warning on close

Usage

1. Download localsheets.html
2. Open it in Chrome, Edge, Brave, or Safari (see Browser support below; Firefox is not officially supported in v1.1)
3. Start typing. That's it

No install. No npm. No build step. No telemetry.

Keyboard shortcuts

Formula reference

Start a formula with =. Function names are case-insensitive. Cross-sheet refs use SheetName!A1 or 'Sheet Name'!A1.

Math / Stats: SUM, AVERAGE, COUNT, COUNTA, COUNTBLANK, MIN, MAX, MEDIAN, STDEV, VAR, PRODUCT, ROUND, ROUNDUP, ROUNDDOWN, FLOOR, CEILING, INT, MOD, ABS, SQRT, POWER, EXP, LN, LOG, LOG10, PI, RAND, RANDBETWEEN, SIGN

Logical: IF, IFS, SWITCH, IFERROR, IFNA, AND, OR, NOT, XOR

Text: CONCAT, CONCATENATE, TEXTJOIN, LEN, UPPER, LOWER, PROPER, TRIM, LEFT, RIGHT, MID, FIND, SEARCH, SUBSTITUTE, REPLACE, REPT, VALUE, TEXT, EXACT

Lookup: VLOOKUP, HLOOKUP, INDEX, MATCH, XLOOKUP, ROW, COLUMN, ROWS, COLUMNS

Conditional aggregates: SUMIF, COUNTIF, AVERAGEIF, SUMIFS, COUNTIFS, AVERAGEIFS

Dates: TODAY, NOW, DATE, YEAR, MONTH, DAY, WEEKDAY, EOMONTH, EDATE, DATEDIF, DAYS, NETWORKDAYS

Financial: PMT, FV, PV, NPV, IRR

Info: ISNUMBER, ISTEXT, ISBLANK, ISERROR, ISERR, ISNA, ISLOGICAL, N

Inline charts: SPARKLINE: =SPARKLINE(A1:A10) returns an inline SVG line chart in the cell. Optional 2nd arg "bar" for a bar variant; optional 3rd arg is a hex color like "#ef4444".

Cell references: plain A1 (relative), $A$1 (both absolute), $A1 / A$1 (mixed). The fill handle preserves absolute parts when dragging.

File format

Files are saved as .localsheet.json: plain JSON, fully portable, git-diffable. Multi-sheet schema (v2.0):

{
  "version": "2.0",
  "tool": "localsheets",
  "meta": { "title": "My Budget" },
  "sheets": {
    "sAbc12345": {
      "name": "Sheet1",
      "cells": {
        "A1": { "raw": "Salary", "value": "Salary", "type": "text", "format": { "bold": true } },
        "B1": { "raw": "5000",   "value": 5000,     "type": "number", "format": { "numfmt": "currency" } },
        "B2": { "raw": "=B1*12", "formula": "=B1*12" }
      },
      "colWidths": {}
    }
  },
  "sheetOrder": ["sAbc12345"],
  "activeSheet": "sAbc12345"
}

• Sparse: only populated cells are stored
• Formulas re-evaluate on load: saved files never trust the cached value for formula cells
• v1.0 files (single-sheet cells map) auto-migrate to v2.0 on open

Templates

Seven ready-to-use templates ship in templates/. Open any via the toolbar Open button. See templates/README.md for the full breakdown.

Personal finance

Edge / Robotics

All templates use the v2.0 multi-sheet schema with live formulas that recompute when you edit the inputs.

Local AI (optional)

Click AI in the toolbar to open a panel that talks to a local Ollama instance. No data ever leaves your machine. The panel auto-detects the model list and offers two modes:

• Text reply: freeform response, optionally including the selection as TSV context. Insert into the active cell or paste as TSV below the selection.
• JSON patch: the model returns a structured object like {"A1": "=SUM(B1:B10)", "B12": 42}. The panel validates every cell key, shows a preview, applies as a single undoable bulk action.

Use cases that work well: "categorize these expenses into Needs/Wants/Savings", "explain this formula", "draft a budget for a $90k salary", "what's the next likely value in this series?".

Hardware

Tested on a 7-year-old laptop with no usable GPU. Slow but correct. On modern hardware where a 7B model fits in VRAM, it's snappier. We chose to verify the floor, not the ceiling. If it works here, it works on whatever you have.

Setup

This is a one-time setup. Because LocalSheets runs from file://, Ollama has to be told to accept browser connections. The full per-OS guide is in OLLAMA_SETUP.md, but the short version:

If the AI panel says "Cannot reach Ollama", see OLLAMA_SETUP.md, which covers troubleshooting and recommended models. There's also a standalone verifier, node e2e/verify-ai-live.js, that runs the same HTTP calls the browser makes (reachability, CORS for Origin: null, text-mode, JSON-patch-mode) and exits 0 on success.

Repository layout

localsheets/
├── .gitignore
├── localsheets.html          ← the app (single-file, ~260 KB, what you ship)
├── README.md
├── LICENSE                   ← MIT
├── CHANGELOG.md
├── templates/                ← 7 ready-to-use sample workbooks (see templates/README.md)
│   ├── README.md
│   ├── monthly-budget.localsheet.json
│   ├── rsu-tracker.localsheet.json
│   ├── startup-burn.localsheet.json
│   ├── rental-cashflow.localsheet.json
│   ├── kids-allowance.localsheet.json
│   ├── mortgage-calculator.localsheet.json
│   └── robot-arm-pid-calibration.localsheet.json
├── src/                      ← un-bundled engine + tests (for review / CI)
│   ├── engine.js             (~1,800 lines: tokenizer + parser + evaluator + 99 fns + SPARKLINE + absolute refs + formula-shift helpers)
│   ├── app-layer.js          (~790 lines: DepGraph + Store including structural ops)
│   ├── test-engine.js        (143 tests)
│   └── test-store.js         (56 tests)
└── e2e/                      ← browser end-to-end tests (dev tooling, NOT shipped)
    ├── README.md
    ├── package.json          (one devDep: @playwright/test)
    ├── playwright.config.js  (Chromium + Firefox + WebKit)
    ├── verify-ai-live.js     (standalone Node script: exercises the real Ollama round-trip end-to-end)
    └── tests/                (render, editing, structural, formulas, persistence, panels)

• Engine has no DOM dependencies: pure compute, fully unit-tested (143/143 pass)
• Store has no DOM dependencies: wraps the engine with state, undo, serialization, and structural ops (56/56 pass)
• UI wires the HTML shell to the Store
• Zero runtime dependencies in the shipped artifact: no React, no jQuery, no charting lib, no npm. The e2e/ test harness uses Playwright but is isolated dev tooling; it never ships to users.
• Run engine + store tests with node src/test-engine.js && node src/test-store.js
• Run browser e2e tests with cd e2e && npm install && npx playwright test

Limits (by design)

What LocalSheets will NOT do

Real-time collaboration. Cloud sync. Pivot tables. Macros / VBA. Image embedding. Sheet protection. Excel format parity (.xlsx import is planned). Multi-user editing. Mobile UI (desktop only by design).

Browser support

The "no Firefox" call is pragmatic, not philosophical. Chrome + Edge cover the audiences that care about a local-first spreadsheet, and the in-place-save UX is a core part of the product that Firefox can't deliver. If there's user demand we'll add it back; PRs welcome.

Known limitations

Honest list of things that are missing or partial, not just unsupported. The first user to hit one shouldn't be surprised.

• Drag-and-drop column or row reordering is not supported. Use Insert + cut/paste, or sort.
• While editing a formula, you can't click a tab on another sheet to pick a reference from there. Type Sheet2!A1 manually, or finish the formula on the current sheet first.
• Sort doesn't update formula references inside the sorted range: if your sort range contains cells that reference each other, those refs will point at the original positions after sort. Put formulas outside the sort range.
• Sort / Fill ignore filter state: they operate on the full populated range, not just visible rows.
• Named ranges use string substitution, so a name that looks like a cell ref (e.g. Q1) will collide. The Names dialog warns about this.
• Conditional formatting is single-rule-per-cell: the first matching rule wins, no rule priority UI yet.
• Fill handle pattern detection covers arithmetic series (1, 2, 3 → 4, 5, 6) and repeats only, no month/weekday/date increment yet.
• Tables: the filter chip on a table header opens the existing column filter, which applies to the whole sheet, not just the table's row range.
• Cell merging is supported, but selection navigation into a merged block lands on the owner cell; arrow keys from inside the merge feel slightly different from Excel.
• Freeze at selection uses the focus cell, so freezing while at A1 is a no-op; select a different cell first.
• Chrome may prompt for clipboard permission on every paste: that's a Chrome security policy, not something this app can override. Edge tends to remember.
• Function names must be exact: =conc(...) returns #NAME?. The right name is CONCAT. No fuzzy match.
• No print view or PDF export. Use the browser's built-in print.
• File System Access API (in-place save) only works in Chromium-based browsers. Safari falls back to a download on every save. (Firefox: see Browser support above; not officially supported in v1.1.)
• Mobile shows a warning splash; touch isn't supported by design.

Roadmap

License

MIT. Yours forever.