# Render-Blocking JavaScript Files in the Node-RED Editor (min.js Bundles Delaying UI Load)

**URL:** https://discourse.nodered.org/t/render-blocking-javascript-files-in-the-node-red-editor-min-js-bundles-delaying-ui-load/99698
**Category:** Core Development
**Created:** [17 November 2025 10:54 UTC](https://discourse.nodered.org/t/render-blocking-javascript-files-in-the-node-red-editor-min-js-bundles-delaying-ui-load/99698 "2025-11-17T10:54:24Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![vidit.khemka](https://avatars.discourse-cdn.com/v4/letter/v/e5b9ba/32.png) [@vidit.khemka](https://discourse.nodered.org/u/vidit.khemka)
#### Post date: [17 November 2025 10:54 UTC](https://discourse.nodered.org/t/render-blocking-javascript-files-in-the-node-red-editor-min-js-bundles-delaying-ui-load/99698/1 "2025-11-17T10:54:24Z")

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Hi Team,

While profiling the Node-RED editor (workflow builder) using Chrome DevTools Performance Recorder, I noticed that several **minified JavaScript files (min.js)** are being loaded in a **render-blocking** manner. This significantly delays the editor from becoming interactive.

I want to understand whether this is expected behavior or if there are recommended optimization paths for reducing render-blocking scripts in the Node-RED editor.

* * *

## **Summary of the Issue**

- During page load, multiple JavaScript bundles appear in **red** in the network waterfall, indicating they are **render-blocking**.
- These scripts must fully download, parse, and execute before the UI can render.
- As a result, the **Largest Contentful Paint (LCP)** is delayed.
- Estimated render-blocking impact (from DevTools): **~3.5 seconds**.

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## **Files Observed as Render-Blocking**

Examples of files flagged by the performance trace:

- `vendor.js`
- `red-debug.min.js`
- `main.min.js`
- `dynamic.min.js`
- `mermaid.min.js`
- Additional Node-RED editor JS bundles (jsonata, infotips, node definitions, etc.)

The waterfall shows all of these downloading and executing before the editor renders.

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## **Evidence**

The screenshot attached shows:

- All red-colored network requests are considered render-blocking.
- DevTools recommendations show an estimated **render-blocking savings of 3.56s**.
- Font loading (e.g., NunitoSans.ttf) also contributes additional blocking time.

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## **What I Want to Understand**

1. **Is it expected that so many editor scripts load synchronously?**  
Does Node-RED rely on blocking script execution order to initialize the editor?
2. **Is there an existing recommendation for optimizing script loading?**  
For example:

- using `defer` instead of synchronous `<script>` tags
- splitting larger bundles
- lazy-loading editor modules
- reducing up-front JS parsing cost

1. **Has this been discussed or optimized in recent versions?**  
Are there any active efforts or guidance for minimizing render-blocking on editor startup?

* * *

## **Request for Guidance**

Any insights on:

- why Node-RED ships these JS bundles in a render-blocking manner,
- whether this is necessary for correct editor initialization, and
- whether there are optimizations I can contribute or configure,

would be very helpful.

I can also share the full performance trace if needed.

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/7/3/730438e1678b83e524afd1a8f3fc6eedf021b1b0.png)

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<div class="post-metadata">

### Author: ![knolleary](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/knolleary/32/3_2.png) [@knolleary](https://discourse.nodered.org/u/knolleary)
#### Post date: [17 November 2025 11:31 UTC](https://discourse.nodered.org/t/render-blocking-javascript-files-in-the-node-red-editor-min-js-bundles-delaying-ui-load/99698/2 "2025-11-17T11:31:02Z")

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> [@vidit.khemka](#):
>
> - why Node-RED ships these JS bundles in a render-blocking manner,
> - whether this is necessary for correct editor initialization, and
> - whether there are optimizations I can contribute or configure,

This is just how it is; no real consideration has been made for making anything async. There may be some small gains possible (mermaid could likely be handled async), but I suspect there are also lots of base line assumptions about what has been loaded before the editor allows for any proper interaction.

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### Author: ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)
#### Post date: [15 February 2026 11:31 UTC](https://discourse.nodered.org/t/render-blocking-javascript-files-in-the-node-red-editor-min-js-bundles-delaying-ui-load/99698/3 "2026-02-15T11:31:29Z")

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