Packet Sizing Utility
MTU & MSS Calculator
Calculate TCP MSS from an interface MTU and estimate payload sizes for IPv4 or IPv6 with optional TCP options.
Instant calculation Local only
Calculate TCP MSS from an interface MTU and estimate payload sizes for IPv4 or IPv6 with optional TCP options.
Last updated: October 1, 2026
This Privacy Policy explains how Fast IP Checking ("the Website") handles information when you visit and use our IP address lookup and network information tools. Our goal is to explain clearly which information is processed by the Website and which third-party services receive data as part of the service.
The core function of Fast IP Checking requires processing your public IP address. When you visit the Website, your IP address is transmitted automatically as part of normal internet communication. In addition:
The Website currently relies on the following third-party services for core IP lookup functionality:
Because these requests are made from your browser, these third-party services necessarily receive your IP address and may process request metadata under their own privacy policies and terms. Fast IP Checking does not control their independent data-handling practices.
Fast IP Checking uses Google Analytics to understand how visitors use the Website, measure traffic, and improve performance and content. Google Analytics may process information such as device and browser information, approximate location derived from IP address, pages viewed, referral information, and interaction data. Google may use cookies or similar technologies for these purposes, subject to Google's own policies and any applicable consent requirements.
Fast IP Checking uses Google AdSense to display advertisements. Google and its advertising partners may use cookies, local storage, device identifiers, or similar technologies to serve, measure, personalize, and limit ads, depending on your region, consent choices, and Google's advertising settings.
Advertising data is processed by Google and its partners under their own privacy policies. Where required by law, consent choices may affect whether personalized or non-personalized ads are shown.
The Website may use browser storage for functional preferences. For example, Fast IP Checking stores your light/dark theme preference in your browser's local storage so the selected appearance can be remembered on future visits. This preference is functional and is not used by Fast IP Checking to build a personal advertising profile.
Third-party services used on the Website, including Google Analytics and Google AdSense, may set cookies or use similar technologies as described above.
The city, region, country, coordinates, timezone, ISP, and related information shown by the Website are inferred from IP-based databases and are approximate only. They do not represent your exact physical address or precise GPS location. Fast IP Checking displays this information in your browser and does not store the lookup result in its own persistent database.
Fast IP Checking does not maintain a persistent database of IP lookup results submitted through the core tool. However, hosting or infrastructure providers may retain standard server logs and security records for their own operational, security, and abuse-prevention purposes. Google Analytics, Google AdSense, ipwho.is, and ipify.org may retain data according to their own policies and settings.
Depending on your location, you may have legal rights relating to personal data, such as rights of access, correction, deletion, objection, restriction, or withdrawal of consent. Some data used by the Website is processed directly by third-party services, so requests concerning data controlled by those providers may need to be directed to the relevant provider.
You may also manage cookies, browser storage, and advertising preferences through your browser settings and, where available, the Website's consent controls or Google's advertising settings.
Fast IP Checking is a general-audience network utility and is not specifically directed to children. We do not knowingly use the Website to request personal information directly from children.
We may update this Privacy Policy when the Website, its third-party services, or applicable requirements change. When we make material updates, we will revise the "Last updated" date shown at the top of this policy.
If you have questions, privacy concerns, or requests regarding this Privacy Policy, please use the Contact Webmaster option available from the header or footer of the Website.
Last updated: October 1, 2026
By accessing or using Fast IP Checking (the "Website"), you agree to these Terms of Service. If you do not agree with these Terms, please do not use the Website.
Fast IP Checking provides free network-information tools and educational content. The Website may display your public IP address, approximate IP-based location, ISP or organization information, IPv4/IPv6 details, and related network data. Some features depend on third-party services and may not always be available.
Information shown by the Website is provided for general informational and diagnostic purposes. IP geolocation is inherently approximate and must not be treated as an exact physical address, proof of identity, or a definitive indication of a person's location.
You agree to use the Website only for lawful purposes. You must not:
Core Website functionality relies on third-party services, including ipwho.is for IP geolocation and ISP/network information, ipify.org for IPv6 detection, and OpenStreetMap map tiles displayed through Leaflet. The Website also uses Google services such as Google Analytics and Google AdSense. Availability, accuracy, data handling, and terms of those services are controlled by their respective providers.
We make reasonable efforts to keep the Website useful and functional, but we do not guarantee that results will always be accurate, complete, current, uninterrupted, or error-free. Network conditions, VPNs, proxies, carrier-grade NAT, mobile networks, API limits, browser restrictions, and third-party outages may affect the information displayed.
The Website may display advertising through Google AdSense and uses Google Analytics to understand Website usage and performance. These services may use cookies, local storage, identifiers, or similar technologies subject to applicable consent requirements and their own policies. Please review our Privacy Policy for more information.
Unless otherwise indicated, original Website text, layout, branding, and custom code are owned by or licensed to the Website operator. Third-party names, libraries, map data, APIs, trademarks, and other materials remain the property of their respective owners.
The Website may link to external websites or services for additional tools, documentation, or information. We are not responsible for the content, security, availability, or privacy practices of third-party websites.
The Website is provided on an "as is" and "as available" basis. To the extent permitted by applicable law, the Website operator disclaims warranties regarding accuracy, reliability, availability, or fitness for a particular purpose and is not liable for losses arising from reliance on Website results, third-party service failures, or use of external links.
We may update these Terms when the Website, its services, or applicable requirements change. The date shown at the top of these Terms will be updated when material revisions are made. Continued use of the Website after an update means you accept the revised Terms.
Questions about these Terms may be sent to contact@fastipchecking.com or through the Contact option available on the Website.
Have a question, found an issue, want to request a correction, or need to contact us about privacy or advertising? Use the form below or email us directly at contact@fastipchecking.com.
How this form works: The form does not send your message through Fast IP Checking's server. Submitting it opens your device's default email application with a pre-filled message addressed to us.