LocalLeet

Run LeetCode testcases locally in your browser using WebAssembly toolchains (Python via Pyodide, C++ via Clang).

LocalLeet runs your LeetCode solutions locally, right in your browser. Skip the queue and get results in moments, so you can try ideas, check edge cases and debug without waiting on LeetCode's servers. It adds a Local button next to LeetCode's Run button. Click it, or press Ctrl/⌘ + Shift + ', and your code runs against every testcase in the Testcase panel, including ones you've added or edited. FEATURES • Python and C++ both run fully offline, using WebAssembly builds of CPython (Pyodide) and Clang • LeetCode-style verdicts: Accepted, Wrong Answer, Runtime Error, Time Limit Exceeded and Compile Error • Output, stdout and a cleaned-up traceback for each case, in a LocalLeet tab next to LeetCode's Test Result tab • Expected outputs are learned from the problem's examples and from your own LeetCode Run and Submit results • Hidden testcases from failed submissions are saved, and one click adds them back to the Testcase panel • Handles plain functions, in-place (void) problems, ListNode/TreeNode, design problems (like LRUCache) and common custom-judge problems • Answers to "return in any order" problems are accepted in any order FEELS LIKE LEETCODE • Python: the usual standard-library imports, typing and sortedcontainers come preloaded • C++: C++23 at -O2, the full standard library including <bits/stdc++.h>, using namespace std, and ListNode/TreeNode. Runtime errors are reported the way LeetCode's sanitizers report them, e.g. "signed integer overflow" or "member access within null pointer" PRIVATE BY DESIGN Your code never leaves your browser. LocalLeet has no servers, no analytics and no account. The compilers and interpreters are bundled with the extension, and remembered expected outputs are kept only in the extension's local storage. You can clear them from the options page. SETTINGS The options page has the per-testcase time limit and a setting to preload the toolchain so your first run starts faster. GOOD TO KNOW • Verdicts are given only for inputs whose expected output is known (examples, or cases you've run or failed with LeetCode's own buttons). For other custom inputs you still see the output, just without a verdict. • C++ compiles to 32-bit WebAssembly, so long is 32 bits; use long long. Exceptions can't be caught, and recursion depth is lower than on LeetCode. • Local run times aren't comparable to LeetCode's runtime numbers. LocalLeet is free and open source (MIT): https://github.com/Cheezer1656/localleet LocalLeet is an independent project and is not affiliated with or endorsed by LeetCode.