What is the format of these error codes?

Each code combines three parts: a category prefix (AUTH, VAL, PAY), a zero-padded sequence number (0001), and a screaming snake-case error name (TOKEN_EXPIRED). Together they form a stable, greppable identifier like AUTH_0001_TOKEN_EXPIRED.

Why use structured error codes instead of plain messages?

A stable code lets clients branch on the error programmatically, lets support search logs precisely, and lets you change the human message without breaking integrations. Free-text messages alone are fragile to match against.

Should the code map to an HTTP status?

Often yes. A category usually has a natural HTTP status (auth maps to 401 or 403, validation to 400, not-found to 404). Document the mapping so clients can rely on both the status and the specific code.

Are the numbers meaningful?

The numbers here are illustrative sequence values within a category. In your real catalog, assign numbers deliberately and never reuse a retired code, so historical logs stay unambiguous.

Is anything sent to a server?

No. The category and error-name pools are bundled with the page and every code is assembled in your browser. Nothing about your choices is uploaded or stored.

Application Error Code Generator

When an API returns “something went wrong”, clients and support are left guessing. A structured error code turns every failure into a stable, searchable identifier. This tool assembles codes from a category prefix, a numeric sequence, and a descriptive name, giving you a consistent scheme to build an error catalog around.

How it works

Each code has three parts joined by underscores. The category prefix groups errors by domain (AUTH, VAL, PAY, RATE, NF). The numeric code is a zero-padded sequence number within that category, for example 0001, keeping codes sortable and leaving room to grow. The error name is a screaming snake-case description (TOKEN_EXPIRED, MISSING_FIELD). The generator only pairs names with the category they belong to, so a payment category yields payment-specific names rather than random ones.

Tips and example

Sample output for the auth category:

AUTH_0001_TOKEN_EXPIRED
AUTH_0004_INVALID_CREDENTIALS
AUTH_0007_MFA_REQUIRED

Pair each code with an HTTP status and a user-facing message in a central catalog. The code is for machines and logs; the message is for humans.
Never reuse a retired code. If an error is removed, leave its number burned so old logs and client branches stay unambiguous.
Keep categories coarse and the number space wide. A handful of clear categories with room to grow beats dozens of overlapping ones.