AJAX (Asynchronous JavaScript plus XML) is characteristically unfriendly to search engines, and thus possibly will thwart Search Engine Optimization efforts.

Asynchronous JavaScript is a set of techniques that consent to websites to act more like client-side applications by fetching data as well as processing it locally based upon user actions. Such as, a web-based spreadsheet might allow the user to sort data by diverse columns by reordering locally by means of JavaScript. Otherwise a website could provide a stretchy outline when users click on a heading by eye-catching the heading's contents only once they are opened.

The difficulty with these techniques is that they can conceal content from search engine spiders which do not characteristically process JavaScript. If there is content that is only displayed as a result of actions that have need of Asynchronous JavaScript plus / JavaScript, then it will not be indexed otherwise ranked. This problem is not restricted to data that is downloaded successive to the initial page fetch; content that accompanies that page but that is "hidden" by JavaScript otherwise CSS until specific user actions are taken might also be invisible otherwise ignored by the spiders that might construe invisibility as an attempt at cloaking.

The easiest way to avoid the prospective pitfalls of Asynchronous JavaScript plus is to simply keep away from it entirely. As a universal rule, if you avoid JavaScript as well as CSS properties that hide text, it can be indexed. If your web applications call meant for Asynchronous JavaScript plus and you still want the satisfied to be indexed, the best strategy is to provide a second display mechanism that does not make use of Asynchronous JavaScript plus.

Asynchronous JavaScript plus techniques offer web designers as well as developers powerful functionality that extend rich desktop features to the web. Nevertheless caution should be exercised to ensure that such techniques do not restrain search engine spiders.