> For the complete documentation index, see [llms.txt](https://docs.augelab.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.augelab.com/function-blocks/blocks-reference/data-logic/data-operations/is-none.md).
# Is None
A simple utility block that checks whether a given value is missing (None) and returns a boolean result. Use it to guard logic and prevent errors when a previous block may not provide a value.
## đĨ Inputs
`Generic` A value to check. This can be any data type or image output from another block.
## đ¤ Outputs
`Boolean` True when the input is None, otherwise False.
## đšī¸ Controls
This block has no user-configurable controls.
## ⨠Features
* Straightforward presence check for any incoming data.
* Useful to drive conditional flows or to trigger fallback behavior.
* Lightweight and safe to place before blocks that require valid data.
## đ Usage
* Connect the output of any block to the `Generic` input to test whether that block currently provides a value.
* Use the `Boolean` output to control logic blocks (for example to gate processing, reset flows, or enable fallback actions).
* Place this block before blocks that would fail or produce unwanted results when fed with missing data.
## đ Evaluation
When evaluated, the block returns a single boolean value indicating whether the provided input is missing. This output can be used immediately in logic operations or to trigger recovery steps.
## đĄ Tips and Tricks
* Combine with `Replace None` to automatically supply a fallback value when the input is missing.
* Use with `Data Memory` to freeze or hold a previously valid value and avoid repeated None propagation.
* Route the result into logic blocks like `Not`, `And`, or `Or` to build complex conditional flows.
* Feed the boolean into `Set - Reset` or `All True` when implementing multi-condition controls or latching behaviour.
* Use `Debug Input` to log or inspect the input before and after the check during setup and troubleshooting.
* When guarding image processing chains, pair with visualization/export blocks such as `Show Image` or `Image Logger` so you only pass valid images to viewers or file sinks.
## đ ī¸ Troubleshooting
* If the block always outputs True, verify the upstream block is connected and producing data.
* If behaviour is intermittent, consider holding valid values with `Data Memory` or logging inputs with `Debug Input` to see when data is missing.