---
title: Variables in VCL
summary: null
url: https://www.fastly.com/documentation/reference/vcl/variables
---

VCL provides a multitude of predefined variables describing the state and properties of a request, and also provides a mechanism for declaring custom local variables. Custom variables are always scoped to the subroutine in which they are defined, while predefined variables have a variety of different scopes depending on their purpose and content, and their availability is indicated on each variable's reference page.

## Predefined variables

Explore all available variables here:

- [Backend connection](https://www.fastly.com/documentation/reference/vcl/variables/backend-connection/)
- [Backend request](https://www.fastly.com/documentation/reference/vcl/variables/backend-request/)
- [Backend response](https://www.fastly.com/documentation/reference/vcl/variables/backend-response/)
- [Cache object](https://www.fastly.com/documentation/reference/vcl/variables/cache-object/)
- [Client connection](https://www.fastly.com/documentation/reference/vcl/variables/client-connection/)
- [Client request](https://www.fastly.com/documentation/reference/vcl/variables/client-request/)
- [Client response](https://www.fastly.com/documentation/reference/vcl/variables/client-response/)
- [Date and time](https://www.fastly.com/documentation/reference/vcl/variables/date-and-time/)
- [ESI](https://www.fastly.com/documentation/reference/vcl/variables/esi/)
- [Geolocation](https://www.fastly.com/documentation/reference/vcl/variables/geolocation/)
- [Math constants limits](https://www.fastly.com/documentation/reference/vcl/variables/math-constants-limits/)
- [Miscellaneous](https://www.fastly.com/documentation/reference/vcl/variables/miscellaneous/)
- [Rate limiting](https://www.fastly.com/documentation/reference/vcl/variables/rate-limiting/)
- [Segmented caching](https://www.fastly.com/documentation/reference/vcl/variables/segmented-caching/)
- [Server](https://www.fastly.com/documentation/reference/vcl/variables/server/)

Several predefined variables relate to various views of the HTTP exchange: the client request (`req`), backend request (`bereq`), backend response (`beresp`), cached object (`obj`), and client response (`resp`). These are accessible in their respective parts of the VCL lifecycle (for `[R]eading` and `[W]riting`):

| Variable  | recv | hash | hit | miss | pass | fetch | error | deliver | log   |
| --------- | ---- | ---- | --- | ---- | ---- | ----- | ----- | ------- | ----- |
| req.\*    | R/W  | R/W  | R/W | R/W  | R/W  | R/W   | R/W   | R/W     | R/W   |
| bereq.\*  |      |      |     | R/W  | R/W  | R/W   |       |         | R 1️⃣ |
| obj.\*    |      |      | R   |      |      |       | R/W   |         |       |
| beresp.\* |      |      |     |      |      | R/W   |       |         |       |
| resp.\*   |      |      |     |      |      |       |       | R/W     | R/W   |

1️⃣  A small number of `bereq.` variables are available to read in the `vcl_log` subroutine.

## User defined variables

Custom variables must be declared before they are used, usually at the beginning of a subroutine, before any statements. They can only be used in the same subroutine in which they are declared. Fastly VCL does not provide block scope: declarations apply to an entire subroutine's scope even if a variable is declared within a block.

Custom variables must start with `var.` and otherwise consist of characters in the set `[A-Za-z0-9._-]`. The declaration syntax is:

```vcl
declare local var.{NAME} {TYPE};
```

For example:

```vcl
declare local var.gcs_bucket_name STRING;
```

Variables can be any of the valid [VCL types](https://www.fastly.com/documentation/reference/vcl/types). Declared variables are initialized to the zero value of the type:

- `0` for numeric types
- `false` for [BOOL](https://www.fastly.com/documentation/reference/vcl/types/bool/)
- `NULL` for [STRING](https://www.fastly.com/documentation/reference/vcl/types/string/)

You can assign values to custom variables using `set` (custom variables cannot be `unset`):

```vcl
set var.gcs_bucket_name = "production-site";
```