> For the complete documentation index, see [llms.txt](https://hub.bsvblockchain.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hub.bsvblockchain.org/higher-learning/bsv-academy/bsv-theory/transactions/first-seen-rule.md). # First Seen Rule > We need a way for the payee to know that the previous owners did not sign any earlier transactions. For our purposes, the earliest transaction is the one that counts, so we don't care about later attempts to double-spend. > > \- Satoshi Nakamoto, Bitcoin Whitepaper ![](https://3421145409-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FRTEKu4E7Fvtss3GI9CYU%2Fuploads%2Fgit-blob-7c17a12cdd4c7c64dbc261355abad49358cab1bd%2FTheory%20-%20Transactions%20-%20First%20Seen%20Rule.gif?alt=media) Bitcoin is a solution that solves the double spending problem without the need for a centralised decision making system through the use of the ‘First Seen Rule’. This rule states that the first seen transaction that validly spends a given UTXO is the transaction which is accepted by the node. In a case where two conflicting transactions are introduced simultaneously onto the network which each seek to spend the same input coins to different output destinations, the one which reaches the network nodes which have been allocated the most hashpower stands to be the version of the transaction which is written into a block. The other transaction will never be accepted into a block and as such can never become a permanent part of the Ledger. Additional protections can be implemented such as ‘Double Spend Notifications’ which detect and announce double spend attempts to peers on the network including merchants handling the double spends. Because a double spend must occur within a very short window (less than 5 seconds) it is very simple for online and physical merchants to reject transactions that are double spent or even attempted. Learn more about Double spending here: --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://hub.bsvblockchain.org/higher-learning/bsv-academy/bsv-theory/transactions/first-seen-rule.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.