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.

memory-leak-debugging