Fix the regex

About Regex Rescue

Regex Rescue is a short daily puzzle: match the strings that should match, reject the rest. Every day everyone gets the same challenge so you can compare results. Beginner uses multiple choice; Intermediate and Advanced let you type your own pattern.

Why it helps

• Build reflexes for anchors, character classes, and quantifiers.
• Recognize the wrong answers people commonly write.
• Use the related Regex Generator & Tester for real work.

Runs locally in your browser. Progress is stored only in this browser.

What this challenge teaches

Fix the regex is a short drill for regular expression validation. You are reviewing a form validator and need to match valid IDs while rejecting lookalikes, missing delimiters, and accidental broad matches.

Example reasoning path

• Read the prompt and identify the artifact type before looking at the answer choices.
• Compare the expected target with each candidate result and eliminate options that are only formatting changes.
• Watch for greedy patterns, unescaped dots, missing anchors, and character classes that accept too much.

After you solve it

Open Regex Tester to apply the same skill to your own data. For a broader practice loop, return to Skill Challenges or open Workflow Gallery when the task needs multiple tools.

Challenge state stays local to this browser. Do not paste production secrets into practice prompts.

Practice notes for real projects

Use this page as a warm-up before touching real project data. Read the prompt, write down the signal you are looking for, and only then compare answer choices. That habit carries over to production debugging, where the first visible error is often a symptom rather than the root cause.

After the challenge, recreate the same pattern in the linked tool with a harmless sample. For example, replace real tokens, user identifiers, hostnames, and request bodies with safe values, then verify that the same reasoning still works. This keeps practice useful without exposing private data.

• Save time by checking the smallest artifact that reproduces the issue.
• Write one sentence explaining why the wrong answers fail; that explanation is the skill to reuse later.
• If the challenge involves security, treat decoded or inspected data as untrusted until a separate verification step confirms it.

Quick review prompt

Before replaying the challenge, explain the rule in plain language: what input pattern matters, what output shape is expected, and which mistake would cause the wrong answer. That short explanation makes the drill useful outside the game, because it turns a one-click answer into a reusable debugging checklist for code review, QA notes, and incident follow-up.