Find usage methods, FAQs, and contact channels to quickly resolve your questions while using How Long.
Language switching, language memory, account-related questions
How to search and read, how to find reliable answers
Content sources, update mechanisms, how to contribute content
Privacy protection, terms, disclaimers, and cookies
Error correction, reporting, feature suggestions, and cooperation
Email and social media contact information
You can switch through the language switcher in the top right corner or the language selector at the bottom of the page. We will remember your selected language in your browser.
We integrate authoritative sources (standards, academic papers, institutional guidelines, brand descriptions) with real experiences, and clearly define applicable conditions and ranges; content is continuously updated.
Currently, you can submit content leads and reference materials by contacting us; we will review and organize them online. More convenient contribution channels will be opened in the future.
You can send us an email through "Contact Us" or leave a message on social media. Please provide sources and evidence information as much as possible for us to process quickly.
We follow the principle of data minimization, only store necessary information, and provide deletion and access rights. For details, please check the privacy policy and terms of service.
Currently, no registration is required to browse most content. Future features related to favorites and subscriptions may require login to ensure a personalized experience.
Contact our support team or communicate with us on social media, and we will reply as soon as possible.