Fintech Toolbox: A Free Browser-Based utilitiy for Engineers in finance

If you've ever stared at a raw ACH file trying to figure out why a batch is getting rejected, or scrambled to check whether you've missed the Same Day ACH cutoff, this tool is for you.
I built Fintech Toolbox a free, browser-based utility for anyone who works with ACH files. No login, no install, no data leaves your browser. Just open it and start working.

Why I Built This

ACH files are not meant to be read by humans. Every record is a fixed-width 94-character line with no delimiters, no labels, and no mercy.
The workarounds are universally painful. You paste the file into Excel, full with magic to extract the data you want. Or you pull out a one-off Python script that someone wrote two years ago that half-works for PPD, but falls apart on IAT. Or you just open the NACHA spec PDF and count characters with your finger.
I had a rough first version of this tool that I found very useful in my day-to-day work, but it accumulated enough shortcuts and compromises that I decided to do a full rewrite - cleaner parsing engine, proper validation rules, better UI. The result is what you're reading about now.
I also wanted something local. Data privacy is paramount in finance, so it is best if the data does not even leave your computer. The tool is safe to use for production data, nothing you put in leaves your browser or computer.

What's Inside

ACH File Parser

Paste or drop an ACH file and get a fully structured, interactive breakdown of every record — file headers, batch headers, entry details, every addenda type, batch controls, and file controls.
Every field is displayed with its name, description, inclusion requirement (mandatory/required/optional), and raw value. Supports standard SEC codes: PPD, CCD,WEB, IAT, and more. There are are even some examples built in for testing.

The parser is sprinkled with some helpful magic like nicely formatted dates and monetary amounts, inline helpful tooltips and an easy way to search among the entries or copy any field value.

Real-Time Validation

The validator runs as you type. Errors and warnings appear inline, and clicking any issue jumps you directly to the offending field in the source text.
For issues with a computable correction — wrong check digit, mismatched entry counts or hash totals — there's a one-click auto-fix.

Anonymizer

Need to share an ACH file with a colleague, vendor, or support team without exposing real customer data? The anonymizer scrubs sensitive fields like names, account numbers, individual IDs, addresses and replaces them with deterministic fake, but valid data.
Routing numbers, check digits, amounts, transaction codes, trace numbers, and all control totals are preserved. Every line stays exactly 94 characters. The output is a valid ACH file you can safely share.

ACH Cutoff Times

Live countdown to each of the four Fed ACH processing windows - three Same Day windows and the standard Next Day window. Times are shown in both ET and your local timezone. Settlement date is calculated automatically, accounting for weekends and Federal Reserve holidays through 2027, with upcoming holidays that affect settlement highlighted.

Timezone Converter

A quick multi-timezone converter for coordinating ACH submission deadlines across regions. Pick a time and see it across all relevant zones at once.

Reference Data

All the lookup tables you keep opening tabs for:

• SEC Codes - all Standard Entry Class codes with descriptions
• Return Codes - all R-codes with reason and handling guidance
• Change Codes (NOC) - all C-codes for Notifications of Change
• Transaction Codes - account type and debit/credit mapping
• Service Class Codes - batch-level debit/credit classification

How It Works (Technical Notes)

The toolbox is built with TypeScript and Vite. Parsing, validation rules, and field definitions are all driven by JSON schema files, which makes the grammar easy to read, diff, and extend. All processing happens client-side, ideal for such a privacy and security sensitive area.

Try It

Fintech Toolbox

Feedback is welcome - reach out directly or leave a comment below.

You might see some ISO20022 stuff on the page as well. I have some basic camt 052, 053 parsers in beta, more top come!