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query string
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What is a query string?
A query string is an extension of a website's URL that sends extra information to a database in key-value pairs. The key defines a data set, and the value is a variable belonging to that set. For example, in a search engine, keywords become the values in the query string used to find results.
A typical query string starts after a URL's first question mark (?). Keys and values are separated by an equal sign (=), and multiple parameters are separated by an ampersand (&). For instance:
/search?country=germany&city=berlin&language=german.Query strings can track where visitors come from using Urchin Tracking Modules (UTMs). They also present security issues if key-value pairs include sensitive information. Solutions involve using unusual characters or JSON Web tokens (JWT) to protect the data, though this increases the query string's size.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Where can you find a query string in a website address (URL)?
A query string is an extension of a website's URL that sends extra information to a database. You can find it after the first question mark (?) in a URL. The query string comprises key-value pairs separated by an equal sign (=), with multiple parameters linked by ampersands (&). It concludes with a number sign (#) or at the end of the URL.
For example:
/search?country=germany&city=berlin&language=german.These strings are used for various purposes, such as search engine queries, tracking the origin of website visitors, and monitoring a visitor's navigation path.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What is the main purpose of a query string?
A query string is an extension of a website's URL that sends extra information to a database in key-value pairs. The key defines a data set, while the value is a variable belonging to that set.
Query strings are useful for various purposes:
* Search engines use query strings to generate results based on entered keywords.
* Websites employ query strings, such as Urchin Tracking Modules (UTMs), to track the sources of their visitors, like identifying traffic from Facebook ads.
* They can also track a visitor's navigation path by appending unique identifiers to subsequent query strings.1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How are query strings formatted within a URL?
Query strings are extensions of URLs that send extra data to a database in key-value pairs. The key defines a data set, while the value is a variable within that set.
A typical query string starts with a question mark (?) in the URL. Each key and its value are linked by an equal sign (=), and multiple parameters are separated by ampersands (&). The query string ends with a number sign (#) or at the end of the URL. For example:
/search?country=germany&city=berlin&language=german.A key can have multiple values in standard or serialized formats, with values separated by punctuation like semicolons or commas. While these symbols are World Wide Web Consortium (W3C) recommendations, query strings are not standardized, and their maximum length varies by web browser.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are some common uses of query strings in websites or web applications?
Query strings, added to a website's URL, send extra data to a database in key-value pairs. For example, when you enter keywords into a search engine, the keywords become the values in the query string that the search engine uses to find results.
Websites use query strings to track where visitors come from. For instance, a shoe company can track if visitors arrive from Facebook ads by adding a query string marking Facebook as the source. They can also track where a visitor goes next by adding a unique identifier to the query strings generated by the visitor.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How can extra or sensitive information in a query string affect website security or privacy?
Query strings can pose security risks when they contain sensitive information like usernames and passwords. A common solution is using randomly generated characters for key-value pairs, making it nearly impossible to guess valid values, though this doesn't completely secure the data. Another option is placing all data in a JSON Web token (JWT), which is a base-64 representation of the data protected by a signature. This encoding makes tampering with the query string's data impossible because the parameters are tied together and cannot be altered without detection, but it increases the query string’s size.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
query string, extension of a website’s uniform resource locator (URL) that sends additional information to a database. The information within the parameters is sent in the form of key-value pairs (sometimes referred to as field-value pairs, name-value pairs, or attribute-value pairs). The key is a constant defining a data set (e.g., country). The value is a variable belonging to that set (e.g., Germany).
One example of using a query string is the act of entering key words into a search engine. The key words are used as the values of the query string that a search engine generates to find results. How those parameters are used—or even if they are used—depends on the website that receives the query string. A server may respond by either reading a file from its system or processing the query string according to logic specifically reserved for the requested resource.
A standard query string typically starts after a URL’s first question mark (?). Each key and its corresponding value are separated by an equal sign (=). If there are multiple parameters, an ampersand (&) is placed between each set. The query string ends either with a number sign (#) or at the conclusion of the URL. Such a path with a query string might appear like this: /search?country=germany&city=berlin&language=german.
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One key can usually be linked to multiple values. In such cases, the key-value data’s format can be standard (e.g., ?key1=value1&key1=value2) or serialized. In a serialized format, each value is separated from the others by punctuation such as a semicolon (;) or a comma (,). For example, the key “country” might be followed by the required equal sign and then “germany;bahrain;mexico.”
Query strings are not standardized. The traditional symbols are only recommendations of the World Wide Web Consortium (W3C), and the maximum length of query strings varies by Web browser.
Query strings allow websites to track where their visitors come from. For example, an online advertisement for shoes, once clicked, will send a URL to the shoe company’s website, which will bring the visitor to that site. Query strings employed for this purpose are called Urchin Tracking Modules (UTMs). If the online advertisement is on Facebook, the shoe company may append a query string to that URL marking Facebook as the source (e.g., ?source=facebook). The shoe company can thus learn how many of its visitors arrive due to its Facebook ads as opposed to those it posts on other sites.
Query strings can also be used to track where a visitor goes next. When a URL is read by a website, the site can append a unique identifier to the query strings generated by the visitor thereafter. This identifier can be invisibly tracked by the website or a third party.
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Query strings present security issues in that key-value pairs sometimes include sensitive information, such as usernames and passwords. One common solution to this vulnerability is the use of unusual or randomly generated sets of characters for key-value pairs. This method does not seal off the data, but it does makes it virtually impossible to guess parameters’ valid values. Another option is to place all the data in a JSON Web token (JWT), which is a base-64 representation of the data protected by a signature. When thus encoded, tampering with the query string’s data is impossible; the parameters are tied together and cannot be altered without being detected. The drawback is that this technique naturally increases the query string’s size.