Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsWhen Angular’s development server runs with hot module replacement (HMR) enabled, it fetches all @defer block dependencies eagerly instead of waiting for the block’s configured loading triggers. The block’s main content still renders according to its trigger; eager fetching does not mean the content appears immediately. To test trigger-dependent loading in development, serve the app with --no-hmr.
What NG0751 means
Angular’s NG0751 reference explains that HMR eagerly loads all @defer block dependencies, including when the block uses client-only or incremental hydration triggers. HMR is intended to apply code changes at runtime without reloading the entire page; fetching the deferred dependencies supports that runtime component replacement.
This is a development-server behavior, not a description of production loading. Angular’s build-system migration guide describes HMR in the context of development builds.
Fetching dependencies is not the same as rendering the block
Keep two events separate: the browser can download a dependency before its configured trigger fires, while the block’s main content remains governed by that trigger. Angular explicitly says defer-block rendering continues to respect configured conditions when HMR is enabled. So an early network request alone does not show that the block rendered early or that its trigger was ignored.
#1 Best Overall
Compare HMR modes when testing
| Development mode | When dependencies are fetched | What controls visible content | Useful for |
|---|---|---|---|
| HMR enabled | All @defer dependencies are fetched eagerly. |
The configured rendering trigger still applies. | Applying development changes without a full page reload. |
HMR disabled with --no-hmr |
Standard trigger-dependent loading is restored. | The configured trigger applies. | Testing whether dependencies load in response to defer triggers. |
To check trigger-dependent loading, stop the current dev-server session and serve the app with the documented --no-hmr option. The Angular deferred-loading guide documents this switch. Do not infer a production loading pattern from the HMR-on development session.
If dependencies still load eagerly with HMR off
Check whether the dependencies qualify for deferral before treating eager loading as an HMR issue. Angular’s guide says components, directives, and pipes must be standalone, and they must not also be referenced outside @defer blocks in the same file. Non-standalone dependencies are not deferred. The guide also notes that transitive dependencies can still take part in deferred loading even if declared in an NgModule.
- Confirm the dev server was restarted with
--no-hmrand that you are observing the new session. - Check the relevant component, directive, or pipe’s standalone status.
- Search the same file for references to that dependency outside a
@deferblock. - Compare network requests with the block’s rendered content; a downloaded dependency and visible main content are different signals.
How this fits ordinary @defer behavior
Outside the HMR-specific development behavior, Angular’s @defer template feature can split eligible component, directive, pipe, and component-style dependencies into separate JavaScript chunks and load them when needed. It supports triggers, prefetching, and placeholder, loading, and error sub-blocks; the guide says the default trigger is browser idle.
Server rendering has a separate default: with SSR or SSG, Angular uses the placeholder (or renders nothing if no placeholder is defined) and does not invoke defer triggers on the server. On the client, the placeholder is hydrated and triggers activate. Incremental hydration can be configured to render main content on the server; NG0751 specifically identifies HMR’s eager fetching in relation to client-only and incremental hydration triggers.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Quick Recap
Rank #3
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
