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Offline software for small businesses

Affordable, offline-first business tools — documents, PDFs, invoicing, diagrams and data — without subscription lock-in.

Coming soon

Affordable premium, offline-first software. Local-first; no subscription trap. Culltron Max and Ultra X27 (Ultra X27 generation). Affiliate disclosure.

What this covers

Culltron's Max desktop apps are separate products built on one shared, hardened platform. Each keeps its data on your machine and works offline.

The Culltron tools for this job

Books Max

Offline invoicing, quotes, clients, products and expenses. Data stays on your machine, and the core tools need no account or internet.

  • Invoices, quotes, client and product lists, and expense records.
  • An accounting core with exact-decimal amounts, a chart of accounts, balanced append-only journals and trial balances.
  • Corrections made only by reversal, so posted records are never overwritten.
  • Ledger-backed customer receipts and credit notes, posted by explicit confirmed actions.
  • A banking reconciliation inbox: import statements, detect duplicates and confirm matches to invoices or expenses.
  • CSV and JSON export of your records.

Limits: Bank and tax-provider connections stay switched off until approved credentials and launch checks are in place. Close workflows cover a single set of books, not a multi-client practice.

Office Max

Documents, spreadsheets and slide decks in one offline-first desktop app.

  • A rich-text document editor with a structured citation registry, deterministic numbering and a bibliography you can refresh.
  • A spreadsheet formula engine running in the app, with 103 user-facing functions, A1 ranges and dependency recalculation that detects circular references.
  • A slide editor with a Present mode.
  • DOCX and XLSX import with a review step. Before a copy is made, the app shows what will be lost and what is supported. The original file is kept unchanged and is verified by checksum.
  • DOCX and XLSX export of the supported subset, plus local drafts and autosave.
  • A signed offline licence lease, so you can keep working without a connection.

Limits: Imports cover a supported subset; Word citation fields and syncing with external reference managers are not claimed. Import reports are local checksums, not a guarantee of full fidelity.

Data Max

A local SQLite database studio that works fully offline.

  • Create databases and design tables with types, primary keys and foreign keys, then edit data in a grid.
  • Guarded SQL: reads run freely, while a write needs Write mode, a confirmation and a single statement.
  • Group-by reports with charts.
  • CSV and JSON import and export. Import handles comma, semicolon, tab and pipe separators and common encodings. Export is spreadsheet-safe by default.
  • Six templates with sample data: CRM, inventory, invoices, municipal assets, members and projects.
  • Model Pipelines: validated join and aggregate models with built-in data tests and local run receipts.

Limits: Nothing is uploaded and nothing runs on a schedule unattended. Pipelines verify up to 100,000 source rows per run.

Mail Max

An IMAP/SMTP mail client with an offline cache.

  • Several accounts with provider presets, synced in the background into a local cache.
  • A three-pane reader with a strict HTML sanitiser. Scripts are stripped and remote images are blocked by default.
  • Compose, reply and forward with attachments.
  • An outbox with a durable record of each send. Replaying an operation returns its existing state instead of sending again.
  • Local search and conversation threading.
  • Advisory phishing flags.

Limits: SMTP acceptance is recorded per recipient but is not proof of delivery. Mail Max does not resend automatically.

Who it is for

How it works

  1. Each Max app is a separate desktop product built on Culltron's shared, hardened platform.
  2. Files and records stay in a local folder on your machine, and the core tools work offline.
  3. A signed licence lease unlocks the paid edition. Ultra X27 adds advanced features that the server enforces.
  4. When you change a file, the app writes a new copy, often with a checksum receipt, instead of silently overwriting your original.

Frequently asked questions

Is this one big bundle?

No. Each Max app is a separate product with its own full editor and local workspace.

What happens to my data if I stop paying?

Records export in open formats such as CSV, JSON, DOCX, XLSX, SVG and PNG.

Are the installers signed?

Not yet. Public downloads stay gated until signing and release approval.

Where can I get help?

See the Help Centre and the Support page.

Release status: built and tested in the repository. A public download appears only after signing, checksum verification and release approval; see Downloads.