--- name: memory-leak-debugging description: Diagnoses and resolves memory leaks in JavaScript/Node.js applications. Use when a user reports high memory usage, OOM errors, or wants to capture, compare, or inspect heap snapshots with Chrome DevTools MCP memory tools. --- # Memory Leak Debugging This skill provides expert guidance and workflows for finding, diagnosing, and fixing memory leaks in JavaScript and Node.js applications using Chrome DevTools MCP tools. ## Prerequisites Advanced memory debugging tools (`compare_heapsnapshots`, `get_heapsnapshot_details`, etc.) are only available when the server is started with the `--memoryDebugging` flag. First check if these tools are available; if not, try to read the MCP configuration file to check if `--memoryDebugging` is enabled. ## Core Principles - **Prefer MCP memory tools:** Do NOT attempt to read raw `.heapsnapshot` files directly, as they are extremely large and will consume too many tokens. Use the Chrome DevTools MCP heap snapshot tools to summarize, compare, and inspect snapshots. - **Isolate the Leak:** Determine if the leak is in the browser (client-side) or Node.js (server-side). - **Common Culprits:** Look for detached DOM nodes, unhandled closures, global variables, event listeners not being removed, and caches growing unbounded. _Note: Detached DOM nodes are sometimes intentional caches; always ask the user before nulling them._ - **Close Loaded Snapshots:** Heap snapshots can be large. After completing an investigation, use `close_heapsnapshot` for each loaded snapshot to release memory held by the MCP server. ## Workflows ### 1. Capturing Snapshots When investigating a frontend web application memory leak, utilize the `chrome-devtools-mcp` tools to interact with the application and take snapshots. - Use page-scoped tools like `click`, `navigate_page`, `fill`, etc. (specifying `pageId`) to manipulate the page into the desired state. - Revert the page back to the original state after interactions to see if memory is released. - Repeat the same user interactions 10 times to amplify the leak. - Use `take_heapsnapshot` (with `pageId`) to save `.heapsnapshot` files to disk at baseline, target (after actions), and final (after reverting actions) states. ### 2. Comparing Snapshots Once you have generated `.heapsnapshot` files using `take_heapsnapshot`, compare them with Chrome DevTools MCP memory tools. - Start with `get_heapsnapshot_summary` for each snapshot to confirm that the files load and to compare high-level totals. - Use `compare_heapsnapshots` to compare baseline and target snapshots. Start without `classIndex` for the summary diff, then request detailed class diffs only for suspicious growth by specifying `classIndex`. - Use the summary output from `compare_heapsnapshots` before drilling into specific node IDs. ### 3. Inspecting Retainers and Dominator Chains When a class or object type grows unexpectedly, inspect the retaining chain and dominators with the MCP tools before changing code. - Use `get_heapsnapshot_class_nodes` to list instances of the suspicious class. - Use `get_heapsnapshot_retainers`, `get_heapsnapshot_retaining_paths`, `get_heapsnapshot_dominators`, and `get_heapsnapshot_edges` to understand why representative nodes are still reachable. - Use `get_heapsnapshot_object_details` with a specific `nodeId` to retrieve detailed object metadata (size, type, distance, and DOM detachedness). - Use `get_heapsnapshot_duplicate_strings` when string growth dominates the diff. - Read [references/common-leaks.md](references/common-leaks.md) for examples of common memory leaks and how to fix them after the retaining path points at application code. ### 4. Advanced Analysis and Categorized Filters Use built-in MCP memory tools and filters to pinpoint specific leak categories directly without external tools. - Use `get_heapsnapshot_details` or `get_heapsnapshot_class_nodes` with `filterName` to target common leak causes: - `objectsRetainedByDetachedDomNodes`: Identifies detached DOM elements retained in memory. - `objectsRetainedByEventHandlers`: Identifies objects kept alive by unremoved event listeners. - `objectsRetainedByContexts`: Identifies objects trapped in closures or execution contexts. - `objectsRetainedByConsole`: Identifies objects retained by console logging. --- Source attribution: ChromeDevTools Original project: https://github.com/ChromeDevTools/chrome-devtools-mcp License: MIT License information: https://opensource.org/license/mit Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice MIT License Copyright (c) 2026 Gabriel Moreira Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. # Mega AI Hub resource metadata Creator / publisher: ChromeDevTools Original project: https://github.com/ChromeDevTools/chrome-devtools-mcp Attribution basis: Upstream repository explicitly recorded in package mirror path Fields of work: Development & Engineering, Customer Support Roles: Backend Developer, DevOps / SRE, Frontend Developer, QA / Test Engineer, Technical Support Specialties: Backend, Frontend Tools: Memlab Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: 895127ac55a3f2c4e0ca9be496e84165eee6408637c2bcc5516d69170a8de80e