An HTTP status code reports how a server handled a request. Use the FindUtils HTTP Status Code Lookup to search the reference by number, name, or keyword. Read the response body and service documentation before you decide the cause of an error.
What Are HTTP Status Codes?
HTTP status codes are standardized three-digit numbers returned by a web server in every response. They communicate the outcome of the client's request -- whether it succeeded, was redirected, or failed. The codes are defined across several RFCs (including RFC 9110) and maintained in the IANA HTTP Status Code Registry.
Every code falls into one of five categories based on its first digit:
| Capability | FindUtils |
|---|---|
| 1xx Informational | Gray |
| 2xx Success | Green |
| 3xx Redirection | Blue |
| 4xx Client Error | Amber |
| 5xx Server Error | Red |
A 4xx response reports a client-error condition. A 5xx response reports a server-error condition. The status alone does not establish the root cause.
How to Use the HTTP Status Code Lookup
Step 1: Open the Tool
Navigate to the HTTP Status Code Lookup. All 62 status codes are displayed as expandable cards, sorted numerically and color-coded by category.
Step 2: Search by Number, Name, or Keyword
Type into the search field to find a specific code. The fuzzy search (powered by Fuse.js) works multiple ways:
- By code number: Type
404to jump to Not Found - By name: Type
bad gatewayto find 502 - By keyword: Type
redirectto see all redirection codes, ortimeoutto find both 408 and 504
Results update in real time as you type.
Step 3: Filter by Category
Use the category dropdown to narrow results to a single group. Select "4xx Client Error" to see only client errors, or "3xx Redirection" to focus on redirect codes.
Step 4: Expand a Code for Details
Click any card to expand it. The expanded view shows two panels:
- When It's Used -- A real-world scenario where this code appears
- How to Fix -- Actionable steps to resolve the issue
Step 5: Clear Filters and Browse
Click "Clear filters" to reset and browse all 62 codes sequentially, building familiarity with less common entries like 206 Partial Content, 409 Conflict, or 428 Precondition Required.
Quick Reference: Most Common Status Codes
| Code | Name | When You See It |
|---|---|---|
| 200 | OK | Standard success response |
| 201 | Created | POST that creates a new resource |
| 204 | No Content | Successful DELETE or update with no body |
| 301 | Moved Permanently | Resource has a permanent replacement URI |
| 302 | Found | Temporary redirect |
| 304 | Not Modified | Browser cache is still valid |
| 400 | Bad Request | Malformed JSON, missing fields |
| 401 | Unauthorized | Missing or expired authentication |
| 403 | Forbidden | Server refuses the request; authentication is not implied |
| 404 | Not Found | Resource does not exist |
| 422 | Unprocessable Content | Valid syntax but failed validation |
| 429 | Too Many Requests | Rate limit exceeded |
| 500 | Internal Server Error | Unhandled server exception |
| 502 | Bad Gateway | Proxy got invalid response from backend |
| 503 | Service Unavailable | Server overloaded or under maintenance |
| 504 | Gateway Timeout | Backend too slow through proxy |
Commonly Confused Status Codes
400 vs. 422
A 400 Bad Request means the request is syntactically malformed -- broken JSON, missing header, or invalid URL. A 422 Unprocessable Content means the syntax is fine but the data fails semantic validation -- invalid email format, inverted date range, or nonexistent foreign key. Use 400 for parsing failures and 422 for business logic validation.
401 vs. 403
401 Unauthorized is about authentication -- the server does not know who you are. Provide valid credentials and the request may succeed. 403 Forbidden means the server understands the request but refuses it. It does not prove that authentication succeeded.
301 vs. 302 vs. 307 vs. 308
All four are redirects, differing on permanence and method preservation:
| Code | Permanent? | Preserves HTTP Method? |
|---|---|---|
| 301 | Yes | No (may change POST to GET) |
| 302 | No | No (may change POST to GET) |
| 307 | No | Yes |
| 308 | Yes | Yes |
For SEO URL changes, use 301 or 308. For temporary API redirects where POST must stay POST, use 307.
502 vs. 504
502 Bad Gateway means the proxy received an invalid response -- the backend likely crashed. 504 Gateway Timeout means the proxy received no response within its timeout -- the backend is too slow. For 502, check if the backend is running. For 504, optimize slow queries or increase the proxy timeout.
FindUtils vs. Alternative HTTP Status Code References
| Capability | FindUtils |
|---|---|
| Total codes covered | 62 |
| Search by number | Yes |
| Search by name/keyword | Yes (fuzzy) |
| Filter by category | Yes (dropdown) |
| Use case per code | Yes |
| Solution per code | Yes |
| Color-coded categories | Yes (5 colors) |
| Expandable detail cards | Yes |
| or signup | Yes |
FindUtils combines fuzzy search, category filtering, and inline use-case/solution panels in a single-page interface. Other references require navigating to separate pages for each code. The FindUtils lookup keeps everything on one page with instant search -- ideal when you are mid-debugging.
Practical Debugging Scenarios
API Returns 422 on a Valid-Looking Request
Valid JSON alone does not rule out a 400 response. An API can reject other parts of the request. Expand the 422 card in the lookup tool to confirm: the data is syntactically correct but semantically invalid. Check the response body for validation errors -- duplicate emails, weak passwords, or nonexistent referenced IDs.
Nginx Returns 502 After Deployment
The reverse proxy received an invalid response from the upstream. Your application likely crashed on startup. Check application logs for missing environment variables, failed migrations, or syntax errors in new code.
Rate-Limited by a Third-Party API
A 429 means you exceeded the rate limit. Check the Retry-After header, implement exponential backoff, review X-RateLimit headers, and cache responses to reduce request frequency.
Redirect Loop (ERR_TOO_MANY_REDIRECTS)
Search "redirect" in the lookup to review all 3xx codes. The issue is usually a 301 or 302 where Page A redirects to Page B and back. Check server configuration for conflicting HTTPS and non-www redirect rules.
Privacy and Performance
The HTTP Status Code Lookup is fully client-side. All 62 codes are bundled into the page with no API calls on search or filter:
- Local lookup — The search works against the bundled reference list.
- Works offline -- once loaded, everything works without internet
- Instant results -- Fuse.js runs locally with zero latency
- No rate limits -- search as many codes as you want
FAQ
Q1: How many HTTP status codes does the tool include?
The tool contains a selected reference list. Consult the IANA HTTP Status Code Registry for registrations, reserved entries, and current references. The list is not every possible status value.
Q2: What is the difference between 401 and 403?
A 401 means you need to authenticate (provide credentials). A 403 means the server refuses the request. Check authorization and server policy; the code does not prove that authentication succeeded.
Q3: What does a 502 Bad Gateway mean?
A reverse proxy or gateway (like Nginx) received an invalid response from the backend. The backend likely crashed or is not running. Check application logs and verify the backend process is alive.
Q4: Can I search by keyword instead of number?
Yes. Type "redirect" to find all redirection codes, "timeout" for 408 and 504, or "cache" for 304 Not Modified. Fuzzy matching works on numbers, names, descriptions, and keywords.
Q5: Is the tool free and does it work offline?
Yes to both. No account, no API keys. Once the page loads, all functionality works without an internet connection.
Q6: What should I do when I get a 500 Internal Server Error?
A 500 is a catch-all for unhandled server exceptions. Server administrators should check error logs for the stack trace. Users should report the issue and try again later.
Tools Used
- HTTP Status Code Lookup -- Search all 62 HTTP status codes with descriptions, use cases, and solutions
- HTML Entity Finder -- Search HTML entities by name, character, or code point
- MIME Type Finder -- Look up MIME types by file extension or content type
- cURL to Code Converter -- Convert cURL commands to code in multiple languages
- API Docs Generator -- Generate API documentation with proper status code responses
- JSON Formatter -- Format and validate JSON response bodies
