Simple Invoice vs Invoice Ninja

Both products let you keep control of your invoicing data. Invoice Ninja does it by being open source: you can read the code, run it on hardware you control, and export everything. Simple Invoice does it by having no backend: there is nothing to run, and the data sits in your browser's local storage as a JSON document you can export at any time. Ownership through self-hosting is stronger — a server you run keeps working across devices and users — but it is also work. Ownership through a local browser app is effortless and single-device. Local-first vs cloud invoicing apps covers the general trade-off.

Running Invoice Ninja yourself means a server or container, a database, a web server, TLS certificates, email delivery configuration, updates and backups. For someone comfortable with that, it is a rewarding way to get a full invoicing system for the cost of hosting. For everyone else, the hosted service exists — a limited free plan and paid plans on the company's servers — which returns you to the account-and-subscription model, with the reassurance that the software is open and your data exportable. Simple Invoice has no such fork in the road: open the URL and it is running.

Almost everything that needs a server. Invoices are emailed with tracking and reminders; clients pay through a wide range of payment gateways; recurring invoices bill automatically; quotes are sent for approval and converted; a client portal shows every document; expenses, vendors, tasks and time tracking feed into invoices; several users can work in one company. Invoice Ninja also lets you edit the invoice design's markup directly, which gives layout control beyond most hosted apps. It is a substantial product, and its breadth is the point.

It produces the document. Blocks are arranged on screen — header, parties, items, totals, payment details, notes — with six presets and typography and colour options, and the layout is saved as a template. Numbering, totals, taxes, discounts and locale-aware currency and date formatting are handled. Status is tracked; overdue is derived from due dates. The PDF comes from the browser's print engine with explicit pagination. Sharing is a PDF or a link carrying the invoice in the URL fragment. How to make an invoice walks through a first invoice in a couple of minutes.

If you want a complete invoicing system you control end to end and you can run a server — or you are content to pay for hosting of open software — Invoice Ninja is the more capable choice. If you want to produce good invoices now, with no installation, no account and nothing stored off your device, Simple Invoice is the lighter one. Developers often use both: Simple Invoice for personal or side-project invoicing, Invoice Ninja once there are clients paying online and recurring bills to run.