Profiling with Vue DevTools Performance Tab
Recording component updates, identifying unnecessary re-renders, component timing.
Profiling with Vue DevTools Performance Tab is a free Vue Academy lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Vue Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Profile
Before optimizing you must know where time goes. Vue DevTools includes a performance/timeline view that records component renders so you can find wasted work instead of guessing.
Installing Vue DevTools
Install the browser extension or run the standalone app. In Vite projects the vite-plugin-vue-devtools plugin adds an in-app inspector.
npm install -D vite-plugin-vue-devtoolsStarting a Recording
Open the DevTools timeline/performance tab and press record, then interact with your app. Stop recording to capture the render activity for that window.
The Component Render Timeline
Each component render appears as an event on the timeline. You can see when a component re-rendered and how long its render took.
The Commit Graph
A commit is one flush of updates to the DOM. The commit graph shows each commit and which components rendered in it, letting you spot commits that touch far more components than expected.
Component Timing Flame Chart
The flame chart stacks parent and child render durations. Wide bars are slow renders; deep stacks show how rendering cascades through the tree.
Identifying Wasted Renders
A wasted render is a component that re-rendered but produced the same output. These show up as repeated render events whose result did not change the DOM.
Same Output, New Render
A common cause is passing a freshly created object or inline arrow as a prop each render, breaking memoization. The child re-renders even though its visible output is identical.
<!-- new object every parent render forces child update -->
<Child :config="{ mode: 'a' }" />Fixing with Stable References
Hoist constants or wrap derived data in computed so the same reference is passed across renders.
const config = { mode: "a" };
// or: const config = computed(() => ({ mode: mode.value }));Correlating with Interactions
The timeline also records mouse and keyboard events. Line up a slow commit with the interaction that triggered it to find the exact code path to optimize.
Component Inspector Render Count
The component inspector can highlight components as they update. Watching a counter flash on every unrelated state change reveals over-rendering at a glance.
Quick Check
What does the commit graph in the performance tab represent?
Recap
Use the Vue DevTools performance/timeline tab to record renders. The commit graph shows each DOM flush and its rendered components, while the flame chart reveals slow renders. Look for wasted renders - components that re-render without changing output, often caused by unstable prop references - and fix them with hoisted constants or computed.
Frequently asked questions
Is the “Profiling with Vue DevTools Performance Tab” lesson free?
Yes — the full text of “Profiling with Vue DevTools Performance Tab” is free to read here on the web, and the Vue Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Vue Academy course, upgrade to CoddyKit PRO.
What will I learn in “Profiling with Vue DevTools Performance Tab”?
Recording component updates, identifying unnecessary re-renders, component timing. You practise Vue Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Vue Academy?
No prior experience is required. Vue Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Profiling with Vue DevTools Performance Tab” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Vue Academy lesson?
Yes. Every Vue Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- v-memo for Template Memoization
- Profiling with Vue DevTools Performance Tab
- Virtual Scrolling for Large Lists
- Web Workers with Vue