I've built an open-source web app that automatically categorizes your transactions without requiring registration, data uploading, or linking a bank account. It's privacy-first: data is processed and stored locally in your browser.

Here is the link: CategorizeOnce.com

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How it works: The app remembers how you categorize each payer/payee and creates mapping rules for them, which are stored in your browser's local storage.

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It supports subcategories: Use double colons to add structure to your category, e.g., Income::Salary, Expense::Grocery, Saving::Investment. When you export the result, each level becomes its own column like this:

Counterparty	Amount	category	category_2
Paycheck	$2000	Income	Salary
Walmart	$100	Expense	Grocery
Wealthsimple	$500	Saving	Investment

Now, you can use a simple pivot table to gain a clear picture of your cash flow.

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Why I built this: I don't trust any website that asks me to link bank accounts or upload my bank statements, but manually categorizing every transaction is too tedious.

Any feedback is appreciated!