# What happens when server-rendered HTML differs from client-rendered HTML?

> Differences can be harmless or SEO-critical.

Potentially important differences include:

- main content;

- title;

- canonical;

- robots directives;

- structured data;

- internal links;

- language;

- product availability.

Google's JavaScript guidance specifically advises caution with canonical URLs and robots meta tags because JavaScript changes can produce unexpected processing behavior.

The safest architecture is usually to make important SEO signals consistent between the initial HTML and the rendered output.

## Sources

- [Google Search Central — Javascript SEO Basics](https://developers.google.com/search/docs/crawling-indexing/javascript/javascript-seo-basics)

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Answered by Abhinav Krishna (https://www.theseocentral.com/author/abhinav-krishna)
Source: https://www.theseocentral.com/technical-seo-faq/what-happens-when-server-rendered-html-differs-from-client-rendered-html