5 CSV checks before paying contractors in Base USDC (free local-only JavaScript tool)

Description and use

Local CSV validation for Base USDC payouts: a JavaScript tool that detects duplicates, invalid amounts, wrong chains, and spreadsheet formulas before funds are moved.

Problem

Validate Base USDC payout CSVs locally to catch duplicate addresses, invalid amounts, wrong chains, and spreadsheet formula hijacking before funds are moved.

Outcome

The tool identifies 3 errors and 1 formula warning in a sample CSV, reports a partial total of 6.7 USDC, and passes all 37 original and 89 extended tests.

Workflow

• Upload CSV via file picker or paste box
• Parser reads file up to 64 KiB, 500 rows, 8 columns
• Rejects unclosed quotes, NULs, and oversized files
• Detects duplicate EVM addresses case‑insensitively
• Validates USDC amounts to six decimals and converts to atomic units
• Checks chain field against Base identifiers (Base, 8453, eip155:8453) and token against USDC or canonical contract
• Flags any field starting with =, +, -, or @ as a potential formula
• Generates a downloadable JSON report with error codes, positions, counts, and a partial total
• No wallet or transaction is executed

Evidence

A payout CSV looks simple until one recipient address appears twice, one amount has seven decimal places, and another row points to the wrong chain.

Source

I built a free, fully local Base USDC payout CSV checker to catch these input problems before someone moves money.

Source

The checker flags those prefixes in non‑amount columns, including optional memo fields.

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The downloadable JSON report contains error codes, row/column positions, counts and a partial total, not the raw payee addresses or memo contents.

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