Client-side scripting generally refers to the computer programs on the web that are executed on client-side, by the user's web browser, instead of server-side (on the web server). This type of computer programming is an important part of the Dynamic HTML (DHTML) concept, enabling web pages to be scripted that is, to have different and changing content depending on user input, environmental conditions or other variables. Generally client-side scripts are written in languages such as and VBScript.

Client-side scripts are often embedded within an HTML document, but they may also be contained in a separate file, which is referenced by the documents that uses it. Upon request, the necessary files are sent to the user's computer by the web server. The user's web browser executes the scripts and displays the document, including any visible output from the script. Client-side scripts may also contain instructions for the browser to follow if the user interacts with the document in a certain way.