Accessibility and help

You can change how this site looks, use it with a keyboard, and read explanations of technical words. The site can inspect a spreadsheet, but it cannot yet edit or publish one.

Our accessibility target

We use Web Content Accessibility Guidelines (WCAG) 2.2, Level AAA as the design and testing target for every page and future feature. This includes the applicable Level A and AA requirements.

This is a target, not a claim of complete conformance. You can choose to keep an inspected workbook privately and resume it in the same page after signing in again. Its access window is 24 hours; storage deletion may happen later. Closing the page, work not yet uploaded, and inspections without this option still need further work. Session timing, complete authentication flows, and assistive-technology combinations remain open for review. A test that has not been run is not marked as passed.

Read the accessibility checks and remaining limitations.

Change text, colors, and spacing

Open “Display preferences” in the footer at the bottom of any page. Choose a text-and-background color pair, enlarge text up to 200%, or choose the spacious paragraph layout. These changes apply immediately. Reset restores the default display.

Only these display choices are stored on your device. The preference store does not contain account details, passwords, tokens, filenames, or spreadsheet data. If browser storage is blocked, the choices still work on the current page.

You can also use your browser's zoom and operating system's high-contrast or forced-color settings. At high zoom the page becomes a single column. The comparison table may scroll sideways inside its own named region; the surrounding page should not need sideways scrolling.

There is no automatic slide advance, background audio, flashing content, or required motion. With JavaScript disabled, use browser display settings. The inspection app needs JavaScript; pitch navigation also offers links to each slide.

Use a keyboard

Press Tab to move forward through controls. Press Shift + Tab to go back. A visible border shows the focused control.
The first link skips repeated navigation and moves to the main content.
Press Enter to open a link. Press Enter or Space to activate a button. Use the usual arrow keys to choose a select-menu option.
In the pitch, arrow keys navigate slides immediately. Inputs, buttons, links, dialogs and the comparison-table region keep their own keyboard behavior. Use Space, Page Up, Page Down or the scrollbar to read long slides when presentation scrolling keys are off. The collapsed slide index and Previous and Next buttons offer other ways to navigate.
Open full screen with the pitch's button. Escape exits full screen or closes the keyboard-help dialog.

Sign-in and file help

You may use a password manager, paste your password, and use the browser's autocomplete. No puzzle or memory test is added by this site. Verify your email before inspecting a file.

Read the session and privacy notice on the inspection page before signing in. Sign-out and expired sessions clear protected results. Keep your original spreadsheet on your device; the inspection does not alter that original file.

The app accepts an XLSX file within its stated size limit. Error messages explain what to try next. Do not send private workbook content, passwords, or sign-in tokens when asking for help.

Site map

Technical word meanings

“InvariantBook” is the product name. It means a workbook tool that checks rules which should stay true. The name can be read as “in-VAIR-ee-unt book.”

Invariant: A rule that must still be true after an edit, such as a total matching the sum of its rows.
Workbook: A spreadsheet file containing one or more sheets of rows and columns.
Typed plan: A structured request naming the proposed edits, their limits, and the values expected before editing.
Contract: The list of rules that the result must pass. This is a software check list, not a legal contract.
Policy: Rules about which actions are allowed and which approvals or checks are required.
Runtime: The software that carries out the checks. An AI suggestion does not control its decision.
Adapter: A software part that connects the checking process to a particular spreadsheet reader, writer, or calculator.
Candidate: A draft changed copy. It is not yet an approved or published result.
Semantic diff: A change list that describes cell values and workbook structure, rather than only raw file bytes.
Receipt: A record of an engine run and its observed inputs and outputs. A receipt alone is not permission to publish.
Attestation: A record linking evidence to an output. The current hashed records are not digital signatures.
Canonical: Written in one defined, repeatable form, so two equivalent records can be compared.
SHA-256: Secure Hash Algorithm with a 256-bit result: a method for creating a short file fingerprint. It does not prove who created the file.
CAS: Compare and swap: update a stored record only if its earlier version still matches.
API: Application programming interface: a defined way for software programs to communicate.
MCP: Model Context Protocol: a standard way for AI tools to connect to other software.
TAM: Total addressable market: an estimate of everyone who might buy a product.
SAM: Serviceable available market: the part of that market a product could serve.
SOM: Serviceable obtainable market: the part a business might realistically reach.
LO / LibreOffice: LibreOffice, an office-software suite. Its Calc program can calculate spreadsheets.
UNO: Universal Network Objects: the programming interface used to control LibreOffice. The name is not a claim of internet access.
OOXML: Office Open XML: the structured document format used inside common spreadsheet files.
XLSX: A common spreadsheet file format, with filenames ending in .xlsx. It stores document parts inside an archive.
ZIP: An archive format that packages several files together, often using compression.
XML: Extensible Markup Language: text with tags that describe structured data.
JSON: JavaScript Object Notation: a text format for structured data. JSON itself is not executable program code.
CLI: Command-line interface: a way to use software by typing commands.
Alpha / W1 / P0: Early project-stage labels. They do not mean the full product is ready for public transactions.
AI: Artificial intelligence: software that can generate suggestions. Its output is not treated as verification or approval.
UI: User interface: the pages, buttons, fields, and messages that a person uses to interact with software.
MiB: Mebibyte: a unit of file size equal to 1,048,576 bytes. The inspection limit of 8 MiB is 8,388,608 bytes.

Report an accessibility problem

Open an InvariantBook accessibility issue on GitHub. Include the page, browser, assistive technology if relevant, and the step that did not work. GitHub is a separate website and may require an account.