Credit Card Validator
Validate card numbers with the Luhn checksum and detect the brand.
The Credit Card Validator checks whether a card number passes the Luhn checksum — the mathematical test every payment terminal runs — and identifies the likely brand from the leading digits: Visa, Mastercard, American Express, Discover or JCB.
Luhn validation is the first gate in card processing: it catches typos and transposed digits before a number ever reaches the bank. Combined with prefix-based brand detection (Visa starts with 4, Mastercard 51–55 or 22–27, Amex 34/37), it is the exact logic payment forms implement client-side.
Passing Luhn means the number is well-formed — it says nothing about whether a card exists or has funds. This tool is for developers testing payment flows with test numbers. Everything runs locally; never enter real card data on random websites.
4532 0151 1283 0366
✓ Valid format
Looks like Visa · 16 digits
The Luhn algorithm validates the checksum digit — the same check payment terminals run. Passing it means the number is well-formed, not that the card exists or has funds. Never enter real card details on random sites.
How to use the Credit Card Validator
- Enter the card number with or without spaces.
- Read the Luhn verdict.
- Check the detected brand and digit count.
- Watch the formatted grouping update as you type.
- Use only test numbers, never real card data.
Frequently asked questions
What is the Luhn algorithm?
A checksum that doubles alternate digits (from the right), sums them with digit-reduction, and requires the total to end in 0. It catches single-digit errors and adjacent transpositions — the common human mistakes.
How is the card brand detected?
By the issuer identification number prefix: Visa 4, Mastercard 51–55 and 22–27, American Express 34/37, Discover 6011/65/644–649, JCB 35. The detector matches these patterns.
Can this tool check if a card has money?
No — Luhn only proves the number is structurally valid. Verifying a real card requires a merchant authorization, which is a transaction, not a check. Use published test numbers for development.
Related tools
View all developer tools →JSON Formatter & Validator
Format, minify and validate JSON instantly with clear error messages that point at the exact problem.
Dev ToolsJSON Validator
Check if your JSON is valid and find syntax errors with exact line and column.
Dev ToolsJSON Minifier
Compress JSON to its smallest valid form for storage and transport.
Dev ToolsJSON to CSV
Convert a JSON array of objects into a clean CSV file in one click.
Dev ToolsCSV to JSON
Convert CSV (from Excel or Google Sheets) into a JSON array of objects.
Dev ToolsBase64 Encoder
Encode text or files to Base64 — standard or URL-safe — in your browser.