{"uid":"cap_wpGhUuh58fnhUG2penSqj","slug":"fastapi-online-regex-explainer-263267a8","name":"fastapi.online — Regex Explainer","description":"Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding & crypto utilities, date/time calculators, geo/coordinate math, math & finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.","url":"https://api.fastapi.online/regex-explain","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"flags":{"type":"string","maxLength":10},"pattern":{"type":"string","maxLength":500,"minLength":1}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_pCCTZB2rVOc97Ct4WUnG7","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Explains what a regular expression pattern does in plain English, optionally with flags","exampleAgentPrompt":"Can you explain what this regex pattern does in plain English: ^(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*)@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?$, with the 'i' flag?","exampleUseCases":[{"title":"Understanding inherited legacy regex","prompt":"I inherited this regex from old code and have no idea what it does — can you explain it step by step: (\\d{1,3}\\.){3}\\d{1,3}"},{"title":"Learning regex for code review","prompt":"I'm reviewing a pull request and need to understand what this regex pattern does before approving it: ^(?=.*[A-Z])(?=.*[0-9])(?=.*[^a-zA-Z0-9]).{8,}$ — can you break it down?"},{"title":"Debugging a regex that isn't matching","prompt":"My regex [a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,4} with flag 'gi' isn't behaving as I expect — can you explain exactly what it matches so I can spot the issue?"}],"resultDescription":"A plain-English explanation of the regex pattern, describing what each component matches, what the overall pattern is designed to match or validate, and how any provided flags affect behavior.","failureModes":["Empty or missing pattern field returns validation error","Pattern exceeding 500-character limit is rejected","Invalid or unsupported flags string may produce an error or be ignored","Highly complex or ambiguous patterns may yield an incomplete explanation","Payment failure (402) blocks the request if no valid x402 payment or API key is provided"],"whenToPreferThis":"Choose this endpoint when you need a quick, pay-per-call regex explanation without signup, especially in developer pipelines where understanding inherited or third-party regex patterns is needed programmatically. Prefer over asking a general-purpose LLM directly when you want a structured, consistent explanation at low cost ($0.001 USDC) and no authentication overhead.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T19:11:44.767Z","isFirstParty":false}