We didn't bolt AI onto Excel.
We put Excel inside the AI.

That is why it is fast.
3.2 s50,000-row summary 4.4 sdebit/credit reconciliation 1.2 sanomalies found

All done in the time an add-in takes to fix one cell.

Download for Windows See how it works

Windows 10·11 · Excel 2016 or later · Anthropic / OpenAI-compatible / ChatGPT subscription / Ollama

Xside window: real Excel with the per-vendor totals sheet on the left, the AI panel with its tool-call log and approval card on the right
3.2 s50,000-row ledger summed by account and month (Excel time)
32 toolsAllow-listed tools + MCP server tools
5.7 MBThe app itself. Native Rust
0Hidden channels the AI could use to send data out
Compatibility

AI features that used to need Microsoft 365 or cloud Excel, now on the older Excel on your PC.

No Copilot subscription, no cloud upload. Any desktop Excel from 2016 on.

✓Excel 2016✓Excel 2019✓Excel 2021✓Excel 2024✓Microsoft 365 ✗Excel on the web✗Excel for Mac

Xside is not an Excel we built. It uses the Excel already installed on your computer.

The old assumptions

That is just how Excel AI was supposed to work.

Break the assumption

We didn't bolt AI onto Excel. We put Excel inside the AI.

The Excel already on your PC comes inside the app, and the AI drives all of it. No subscription tier. No VBA. No slow add-in.

Why it is different

Your Excel AI tool today. Sound familiar?

We removed six frustrations, one by one. The technical detail sits in small print under each one.

!Upload the file to the web to use AI, then copy the result back

Your Excel. Your file, untouched.

Nothing moves to another screen. The Excel you already use opens right inside the app, with shortcuts, ribbon, formatting and macros all alive. Results are written straight into your workbook.

TechThe app does not build a new Excel. It brings the Excel window already installed on your PC inside the app window. It operates Excel through the official channel (COM) that Windows provides so "other programs can drive Excel". Nothing is installed into Excel.

Real Excel inside the app: ribbon tabs and the per-vendor totals sheet
!Seconds to change one cell. With many rows: "too large"

50,000 rows in seconds. Excel does the math.

We do not send the table to the AI. The AI decides what to do, and Excel reads, writes and calculates at its own speed. A 50,000-row summary in 3.2 s, debit/credit reconciliation in 4.4 s, anomalous-row search in 1.2 s.

TechThe AI does not read and write cell by cell. It exchanges table ranges as one block. Excel does the sums and pivots, and the AI receives only the parts it needs, which saves time and cost. The app itself is a light 5.7 MB. The numbers are measured values.

Tool-call log in the panel: read_range 6 ms, 4 ms, python_run 2,352 ms
!Locked into one AI vendor's subscription, and security blocks that service

You pick the AI. Swap it any time.

Start right away with a ChatGPT subscription, or use an API your company approves, an on-prem server, or Ollama on your PC. On an air-gapped network it runs with no internet.

TechFour ways to connect: Anthropic (API key), OpenAI-style servers (OpenAI, LM Studio, on-prem servers), ChatGPT subscription (browser login), Ollama (on your PC). Small models without tool calling work too. API keys are stored with Windows encryption so only your account can unlock them.

GPT
ChatGPT subscriptionOne browser sign-in
Connected
A
AnthropicAPI key · Claude
Select
API
OpenAI-compatible serverOpenAI · LM Studio · on-prem server
Select
PC
Ollama (your PC)No internet · air-gapped
Select
!The AI trashed the sheet and there is no way back

A checkpoint copy before writing. An approval card for anything risky.

A checkpoint copy is made before the first write of each request, and your original is never auto-saved. VBA, sheet deletion and screen actions show what will happen where, then ask you to allow or deny.

TechCheckpoint copies stay in your user folder on your PC. Approval is remembered by "which tool runs which code", so if the code differs even slightly, it asks again. Screen actions show the target to click (such as a button name) on the card and ask every time.

Two approval cards: click the 'OK' button, enter 'Total' in cell B3, each with Allow and Deny
!Formula hints are all you get. Pivots, macros and Python are still on you

Pivots, Power Query, VBA, even Python. One request.

Say something like "build a monthly pivot by vendor and chart the top 10" and it carries on to the end. The accounting skills first teach it your rules for descriptions, accounts and closing schedules, so it works like it knows accounting.

TechThe AI can use a fixed set of 32 tools and nothing else. Power Query, VBA and Python code is checked before it runs, and commands that reach the internet or other files are blocked. Python 3.13 ships in the installer, so there is nothing extra to install.

python_run approval card: the code to run is visible, with Allow and Deny buttons
!The AI cannot click menus, and cannot connect to internal systems

It sees the screen and clicks. It plugs into your internal tools.

It looks at the ribbon and dialogs on screen, finds what it needs and clicks it. Register an MCP server and internal tools like ERP lookups run under the same approval rules.

TechFor screen actions, the AI takes a screenshot of Excel, looks at it, and finds buttons and menus by name to click. It works only in the Excel window brought into the app, and stops if another window covers it. External tools are registered over MCP (a common standard for plugging tools into AI). Read-only tools run right away, and tools that change things need approval. Connecting to MCP servers across the internet comes in the next version.

MCP server registration card: name, command, arguments, save
Head to head

How is it different from what you use now?

There are four ways to put AI to work on Excel. Three work outside Excel. Only one works inside it.

Item Paste into ChatGPT Excel add-in Browser-grid AI suites Xside
Your Excel, as isAnother windowWeb task paneDifferent programReal Excel, inside the app
50,000-row ledgerPaste limitCell-by-cell, slowBrowser does the math3.2 s / 4.4 s
Pivot · Query · VBAExplains onlyFormula hints at mostPartial imitationNative Excel features
Formats · macrosMust move results backKeptSome breakOriginal file, 100 %
AI choiceOne serviceVendor onlyA few4 options · local Ollama
Where data goesUploads whole sheetVendor cloudConnected AIOnly needed ranges · your choice
If the AI breaks itManual recoveryCtrl+ZEditor undoCheckpoint + per-call approval
Air-gapped networkNoMostly noWith local modelUSB install · on-prem server

Add-in = Copilot, GPT for Excel and the like. Browser-grid AI suites = products that imitate Excel with a browser grid. Other products' cells describe the typical case, and the Xside cells are measured values from the validation record.

Why Windows only

We didn't skip the Mac. A Mac build would be a different product.

Xside's promise is "an AI that drives the real Excel on your PC." That one sentence chose Windows for us. Four reasons.

01

The driver's door exists only on Windows Excel

The official channel Microsoft opened for other programs to control Excel (COM automation) exists only in desktop Excel for Windows. Ranges, formulas, pivots, Power Query and VBA are all reached through that door. Excel for Mac exposes only a narrow AppleScript window, and pivots, queries and the data model are not reachable through it.

02

Hosting the Excel window inside the app is Windows-only too

Xside holds the Excel window inside its own window. Windows lets one program adopt another's window as an owned window; macOS's security model does not allow an app to embed another app's window. On a Mac the best you get is two windows side by side.

03

That channel is where the speed comes from

A 50,000-row summary in 3.2 s happens because ranges move as one block and Excel's engine does the math. Without that channel you either move cells one at a time (the add-in way) or imitate the math in a browser (the web-grid way), and both crawl past tens of thousands of rows. A fast Mac version cannot be built; a slow one isn't worth building.

04

Accounting and finance run on Windows + Excel

ERP integrations, e-invoicing, corporate security agents and air-gapped PCs are almost all Windows. We went first to where the 50,000-row ledgers live.

What it takesWindows ExcelExcel for MacExcel on the web
Official automation channelCOM automationAppleScript, narrowNone (browser sandbox)
Pivots · Power Query · data modelAll of itOut of reachNo
Host the Excel window in-appOwned windowBlocked by the OSNo
Block range transfer (speed)3.2 s / 50k rowsCell by cellCell by cell, round trips
ResultReal Excel, as isAn imitationSame as an add-in

On a Mac?

Today: run Windows and Excel in Parallels or VMware and Xside works inside it as is. A remote Windows PC at the office (Remote Desktop) works too.

Later: if Excel for Mac opens the same channel, Xside follows. Until then we will not ship an "Excel imitation" Mac version under the same name: it would be slower and less compatible.

TechWindows Excel runs as a COM automation server: another process calls Workbook, Range, PivotTable and Query objects directly and exchanges ranges as SAFEARRAY blocks. Excel for Mac's AppleScript dictionary exposes only part of that object model, and macOS has no API for adopting another app's window as an owned window. Excel on the web lives in the browser sandbox where local processes cannot reach it, and add-ins (Office.js) round-trip cell by cell.

How it works

One line to ask. One tap to approve.

  1. Open your ledger and speak

    "Build per-vendor totals on a new sheet." Seven accounting skills first teach the AI your rules for descriptions, accounts and closing schedules.

  2. The AI reads and writes Excel

    It reads only the ranges it needs and writes formulas and tables in one go. The 50,000 rows are never sent to the AI.

  3. Risky steps come as cards

    It shows the code and target cells, and you allow or deny. A checkpoint copy has already been made before that.

Agent
Expenses.xlsxExpenses · 50,001 rows × 54 cols
What should I do?Send
Security

Your data goes only to your PC and the AI you choose.

External access from formulas, queries and VBA written by the AI (WEBSERVICE, Web.Contents, external links) is blocked, and after any screen action the whole workbook is re-checked within 1 second. Excel work you do yourself is not restricted.

Allow list

Anything off the list, the AI cannot even attempt. External tools only through MCP registration and approval.

Checkpoint copy

Before the first write of each request, a copy is saved in your user folder. Your original is never auto-saved.

Signed updates

Only updates with a valid ed25519 signature and SHA-256 are installed, into your user folder with no admin rights.

Download

Xside 0.8.1 for Windows

Windows 10·11 (64-bit) · Desktop Excel 2016 or later · WebView2 · 72.6 MB · Python 3.13 included

Download Xside-Setup.exe

The download link is not connected yet. Install only a file that matches the SHA-256 below.

Xside-Setup.exe 6E4BF82AD81C1FC1A2CEE4AA1E69D336EC84284085CCDE6DD90A8AF5FA5BA052
App binary 89A2CC4DA99977B038FCDF4CB8126D5977FAB6F21AD45A498D4DDF47B99F918A

This build is not code-signed yet. If SmartScreen shows a warning, choose "More info → Run", and verify the file with certutil -hashfile Xside-Setup.exe SHA256.

The installed app and its executable (Ledger.exe) are renamed to Xside from version 0.9.