Should I retry on 502, 503, 504?

Generally yes — they indicate transient upstream problems. Use exponential backoff (1s, 2s, 4s, 8s) with jitter to avoid synchronised retries from many clients. Cap retries at 3–5 to avoid hammering a struggling server.

What's the difference between 401 and 403?

401 means 'you didn't authenticate' (or your token expired) — try re-authing. 403 means 'we know who you are and you can't do this' — re-authing won't help. The tool flags this common confusion.

Is 418 a real status code?

Yes — RFC 2324 (April 1, 1998) defined 'I'm a teapot' as part of HTTP for the Hyper Text Coffee Pot Control Protocol. It's been used in production by Google, Stackoverflow, and many others as a 'we noticed you' easter egg. The IETF has resisted attempts to retire it.

http · status · retry · rfc · live

Explain any HTTP status code

Paste a status code and get meaning, retryability and RFC reference instantly. Lookup is local — no network, no tracking.

Status Code Explainer

Code

502

input

Class

5xx

registered

Retry

yes

idempotent

RFC

—

spec

input · status code

output · meaning

502Bad Gateway

5xx

Upstream server returned an invalid response.

↻ retryable

Quick Start

How to explain a status code

Type any 3-digit code or click a popular preset to see meaning, retry guidance and the canonical RFC.

01
Enter a code
Type a code like 404 or 502.
Lookups reference the IANA registries (MIME, HTTP status, TLDs) bundled at build time — no live network calls, no rate limits, no leaked queries.
inputIANAregistryofflinelive
input · querycode · IANA
```
502
```
loaded · IANA bundlespec · ready
02
Read the meaning
The canonical name, class (1xx–5xx) and human description appear.
Builders emit canonical syntax per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs) so the output passes spec-compliant parsers.
meaningRFC 9110canonicalspec-compliantlive
name · options502 · live
```
502 Bad Gateway
```
options applied · livecanonical
03
Check retryability
The Retry stat tells you if an idempotent method can be safely retried after backoff.
Validation flags common pitfalls — uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8 — before they bite production.
retryvalidationlintpitfallslive
retry · looked upyes · ready
```
backoff + retry ✓
```
result · livevalidated
04
Copy or cite
Use Copy to grab code text, or quote the listed RFC in docs.
Copy writes the snippet directly into your clipboard; downloads emit the right extension and MIME so curl/httpie pick them up correctly.
citeclipboardMIME-correctblobcurl-ready
ok · copiedready · done
```
Copied 502 Bad Gateway
```
shipped · ready to shipsuccess

Pro tips

Web-spec details that bite later

Idempotency saves retries

POST/PUT/DELETE should be safely retried. Use idempotency keys and return the same response on duplicate requests.

Match RFC 9110 status codes

Don’t invent codes. 422 for validation errors, 409 for conflicts, 429 for rate limits. Standard codes work with off-the-shelf clients.

Set <code>Cache-Control</code> deliberately

Default browser caching is conservative. Use max-age + stale-while-revalidate for hot endpoints.

Validate Open Graph in dev

OG tags break silently. Use a previewer like OG Generator + Facebook’s debugger before launch.

CORS is a server concern

The browser sends the preflight; the server decides. Wildcard origins disable credentials — be explicit.

MIME drives behaviour

Servers must send the right Content-Type. Browsers sniff but the spec says they shouldn’t — be explicit to avoid surprises.

Use Cases

When to explain a status code

Debugging, docs, retry logic.

API debugging

Quickly learn what an unexpected code means. Bundled from IANA registries at build time — no live network call, no rate limit, no leaked queries. The MIME, TLD, and status-code tables are baked in so the tool works offline once loaded.

spec-compliant

Retry policy

Decide between retry / fail-fast / circuit-break. Output is canonical per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs), so spec-compliant parsers accept it as-is. Cross-browser and cross-library behaviour stays consistent.

offline

Docs writing

Cite the canonical RFC text in your error spec. Pairs with the curl-to-fetch converter for end-to-end test stubs — copy the curl from DevTools, paste, get an idiomatic fetch() body. Drop into Playwright/Vitest fixtures without manual translation.

IANA-backed

User-facing copy

Map cryptic codes to friendly messages. Catches common pitfalls (uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8) before they bite production. Validation flags rather than auto-corrects so you stay in control.

RFC-aligned

Onboarding

Help new engineers learn the codespace. Validation runs as you type — copy only when the output is shaped correctly. The output drops directly into nginx, Apache, or CDN configs without re-formatting or re-quoting.

production-grade

Postmortems

Explain why a 502 storm caused user pain. Same input plus same options always produces identical canonical output, so the tool is safe to embed in CI scripts that diff against expected configs.

curl-ready

FAQ

Frequently asked questions

Why is 502 different from 504?

502 means a bad upstream response; 504 means the upstream timed out. Both are usually safe to retry once with backoff.

Are custom codes covered?

No — only standard registered codes. nginx 444 and Cloudflare 520-526 are non-standard and not in the IANA registry.

Should I retry every 5xx?

Retry only idempotent methods with backoff. The Retry stat flags codes the spec calls safe to retry.

Where do the descriptions come from?

Compiled from RFC 9110 + ancillary WebDAV/HTTP/2/3 RFCs.

Is anything sent to a server?

No — the lookup runs locally in your browser.

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