> For the complete documentation index, see [llms.txt](https://docs.stacks.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.stacks.co/reference/~/revisions/swQTSLD6WulC5xzYi5wv/clarity/keywords.md). # Keywords ### block-height {% hint style="danger" %} Deprecated in Clarity 3. {% endhint %} Introduced in: Clarity 1 output: `uint` description: Returns the current block height of the Stacks blockchain in Clarity 1 and 2. Upon activation of epoch 3.0, `block-height` will return the same value as `tenure-height`. In Clarity 3, `block-height` is removed and has been replaced with `stacks-block-height`. example: ```clarity (> block-height u1000) ;; returns true if the current block-height has passed 1000 blocks. ``` *** ### burn-block-height Introduced in: Clarity 1 output: `uint` description: Returns the current block height of the underlying burn blockchain. example: ```clarity (> burn-block-height u832000) ;; returns true if the current height of the underlying burn blockchain has passed 832,000 blocks. ``` *** ### chain-id Introduced in: Clarity 2 output: `uint` description: Returns the 32-bit chain ID of the blockchain running this transaction example: ```clarity (print chain-id) ;; Will print 'u1' if the code is running on mainnet, and 'u2147483648' on testnet, and other values on different chains. ``` *** ### contract-caller Introduced in: Clarity 1 output: `principal` description: Returns the caller of the current contract context. If this contract is the first one called by a signed transaction, the caller will be equal to the signing principal. If `contract-call?` was used to invoke a function from a new contract, `contract-caller` changes to the *calling* contract's principal. If `as-contract` is used to change the `tx-sender` context, `contract-caller` *also* changes to the same contract principal. example: ```clarity (print contract-caller) ;; Will print out a Stacks address of the transaction sender ``` *** ### current-contract Introduced in: Clarity 4 output: `principal` description: Returns the principal of the current contract. example: ```clarity (print current-contract) ;; Will print out the Stacks address of the current contract ``` *** ### false Introduced in: Clarity 1 output: `bool` description: Boolean false constant. example: ```clarity (and true false) ;; Evaluates to false (or false true) ;; Evaluates to true ``` *** ### is-in-mainnet Introduced in: Clarity 2 output: `bool` description: Returns a boolean indicating whether or not the code is running on the mainnet example: ```clarity (print is-in-mainnet) ;; Will print 'true' if the code is running on the mainnet ``` *** ### is-in-regtest Introduced in: Clarity 1 output: `bool` description: Returns whether or not the code is running in a regression test example: ```clarity (print is-in-regtest) ;; Will print 'true' if the code is running in a regression test ``` *** ### none Introduced in: Clarity 1 output: `(optional ?)` description: Represents the *none* option indicating no value for a given optional (analogous to a null value). example: ```clarity (define-public (only-if-positive (a int)) (if (> a 0) (some a) none)) (only-if-positive 4) ;; Returns (some 4) (only-if-positive (- 3)) ;; Returns none ``` *** ### stacks-block-height Introduced in: Clarity 3 output: `uint` description: Returns the current block height of the Stacks blockchain. example: ```clarity (<= stacks-block-height u500000) ;; returns true if the current block-height has not passed 500,000 blocks. ``` *** ### stacks-block-time {% hint style="info" %} This same timestamp can also be retrieved for previous blocks using `(get-stacks-block-info? time height)`, which exists since Clarity 3, but cannot be used for the current block. {% endhint %} Introduced in: Clarity 4 output: `uint` description: Returns the Unix timestamp (in seconds) of the current Stacks block. Introduced in Clarity 4. Provides access to the timestamp of the current block, which is not available with `get-stacks-block-info?`. example: ```clarity (>= stacks-block-time u1755820800) ;; returns true if current block timestamp is at or after 2025-07-22. ``` *** ### stx-liquid-supply Introduced in: Clarity 1 output: `uint` description: Returns the total number of micro-STX (uSTX) that are liquid in the system as of this block. example: ```clarity (print stx-liquid-supply) ;; Will print out the total number of liquid uSTX ``` *** ### tenure-height Introduced in: Clarity 3 output: `uint` description: Returns the number of tenures that have passed. At the start of epoch 3.0, `tenure-height` will return the same value as `block-height`, then it will continue to increase as each tenures passes. example: ```clarity (< tenure-height u140000) ;; returns true if the current tenure-height has passed 140,000 blocks. ``` *** ### true Introduced in: Clarity 1 output: `bool` description: Boolean true constant. example: ```clarity (and true false) ;; Evaluates to false (or false true) ;; Evaluates to true ``` *** ### tx-sender {% hint style="warning" %} Use caution when leveraging tx-sender, as based on the design, you can unintentionally introduce attack surface area. [Read more](https://www.setzeus.com/community-blog-posts/clarity-carefully-tx-sender). {% endhint %} Introduced in: Clarity 1 output: `principal` description: Returns the original sender of the current transaction, or if `as-contract` was called to modify the sending context, it returns that contract principal. example: ```clarity (print tx-sender) ;; Will print out a Stacks address of the transaction sender ``` *** ### tx-sponsor? Introduced in: Clarity 2 output: `optional principal` description: Returns the sponsor of the current transaction if there is a sponsor, otherwise returns None. example: ```clarity (print tx-sponsor?) ;; Will print out an optional value containing the Stacks address of the transaction sponsor ``` *** --- # 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. 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