Cache-Control Expert Guide to HTTP headers

It is a criterion for whether a response is fresh or stale. Store a response in caches when the response is cacheable. It can store and reuse personalized content for a single user. Take back control of your personal information with the browser designed for data protection, not data collection.

The stale-if-error directive allows caches to servea stale response when the origin returns an errorstatus (500, 502, 503, or 504) or isunreachable. The private directive restricts storage to privatecaches, typically the end user’s browser. The proxy-revalidate directive works identically tomust-revalidate, except the requirement applies onlyto shared caches. The response no-transform directive preventsintermediaries from altering the response body beforeforwarding, whether the intermediary caches thecontent or not. When no-cache includes a list of field names,only those specific headers require revalidation.The rest of the stored response is served withoutcontacting the origin. The max-age directive declares the number of secondsthe response remains fresh after generation.

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The way a resource is cached is controlled primarily through HTTP headers, with the Cache-Control header being the most important one. The screenshot below shows an example of the cache control header value for different URLs. A well-implemented caching strategy reduces bandwidth usage, server load, and page load times. If you don’t add a Cache-Control header because the response is not intended to be cached, that could cause an unexpected result. When you 4rabet official website update the library or edit the picture, new content should have a new URL, and caches aren’t reused. You can add a long max-age value and immutable because the content will never change.

As a result, TechCrunch characterized the service as a «hybrid» search engine. The search engine is written in Perl and runs on nginx, FreeBSD, and Linux. DuckDuckGo is an American software company focused on online privacy whose flagship product is a search engine named DuckDuckGo. If you want to change this threshold, you can supply theenvironment variable NOCACHE_MAX_FDS and set it to a higher (or lower) value.It should specify a value one greater than the maximum file descriptor thatwill be handled by nocache. With nocache, the original caching state will be preserved.

This protects sensitive information like passwords and personal data from interception. DuckDuckGo shows the same results to everyone, keeping your searches genuinely open. Whenever you visit a website, third-party trackers from advertisers, data brokers, and social media platforms are trying to collect information about your activity.

• The max-age directive declares the number of secondsthe response remains fresh after generation.
• The max-stale directive signals acceptance of aresponse whose Age has exceeded the freshnesslifetime by up to the given number of seconds.
• DuckDuckGo gives people a way to browse the internet without being subjected to data collection, ad targeting, or website tracking.
• The full picture of what DuckDuckGo offers goes beyond just a search engine.
• DuckDuckGo is a privacy-first search engine and browser that offers a genuine alternative to mainstream services like Google, Yahoo, and Bing.

Cache directives

These directives define seven days as the maximum cache duration, with a one-day window for serving stale content while revalidating. You can click on each one and open the Headers tab to see what response headers, including cache-control, were sent by the server. At the heart of HTTP caching is the Cache-Control HTTP header, which gives you fine-grained control over how browsers and intermediary proxies cache your content.

DuckDuckGo earns revenue by serving ads primarily from the Yahoo-Bing search alliance network. Paragraphs or snippets from any matching articles are returned, and the section that matches the user’s query is highlighted. Longtail Instant Answers are full-text queries to a DuckDuckGo database of articles. Goodies instead use some form of the aforementioned static data sources, such as text files or JSON files. Goodies do not retrieve data from a third-party API, whereas Spices do. These types of Instant Answer extensions are differentiated by how their data is retrieved.

In a statement to Engadget, DuckDuckGo said that The Pirate Bay and Youtube-dl were never removed from its search results if the user searched for those websites using their name or web address. In November 2019, Twitter CEO Jack Dorsey revealed his preference for using the DuckDuckGo search engine rather than Google, stating, «I love @DuckDuckGo. My default search engine for a while now. The app is even better!». Thom Holwerda, who reviewed the search engine for OSNews, praised its privacy features and shortcuts to site-specific searches as well as criticizing Google for «tracking pretty much everything you do», particularly because of the risk of such information being subject to a U.S. government subpoena.

By May 2012, the search engine was attracting 1.5 million searches a day. We invested in it because there is a need for a private search engine. In July 2010, Weinberg started a DuckDuckGo community website (duck.co) to allow the public to report problems, discuss means of spreading the use of the search engine, request features, and discuss open sourcing the code.