> For the complete documentation index, see [llms.txt](https://docs.fastn.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fastn.ai/manage/configs.md).
# Configs
Values your workflow code reads per environment.
**Settings → Configs**
With nothing configured yet, the page reads **No configs yet** above the line that explains the feature:
The Configs page before any config exists. Read a config from workflow code with fastn.envConfig.get("key").
> A config holds anything that changes between test and live, like an endpoint or a feature flag. Read one with fastn.envConfig.get.
```javascript
const endpoint = await fastn.envConfig.get("PARTNER_API_BASE");
const batchSize = await fastn.envConfig.get("BATCH_SIZE");
```
### Creating one
**Add config** opens the **Add Config** dialog, which takes two things.
**Key \*** is the string your code passes: `fastn.envConfig.get("PARTNER_API_BASE")` reads the config whose key is `PARTNER_API_BASE`.
**Values per environment** is one editor per environment, labelled with the display name and the slug: **Test (test)**, **Live (live)**, and a row for each named environment you have added. A value may be raw text or valid JSON.
{% hint style="info" %}
**Leaving an environment's editor blank skips that environment on save**: it does not write an empty value. That is usually what you want when you are only setting up test, but it means a config can silently have no value in live.
{% endhint %}
The same key resolves to a different value depending on which environment the run is in, so your code never branches on environment.
### Configs versus secrets
A config's value is entered and edited in the dashboard rather than written once and hidden, which is the practical difference from a [secret](/manage/secrets.md): you can see what an environment is set to without running anything. Treat that as the working assumption: anything whose exposure would be an incident belongs in a secret regardless.
### Choosing between a config and a secret
| Use a **config** for | Use a **secret** for |
| ------------------------------------------- | -------------------------------------- |
| Base URLs and endpoints | API tokens and passwords |
| Feature flags | Signing and encryption keys |
| Batch sizes, page sizes, thresholds | Database connection strings |
| Anything you would happily show a colleague | Anything whose exposure is an incident |
{% hint style="warning" %}
When in doubt, use a secret. A config that turns out to be sensitive is already visible to everyone who can read settings.
{% endhint %}
### A common pattern
Point test at a sandbox and live at production, without a line of conditional code:
| Config | test | live |
| ------------------ | --------------------------------- | ----------------------------- |
| `PARTNER_API_BASE` | `https://sandbox.partner.example` | `https://api.partner.example` |
| `BATCH_SIZE` | `10` | `500` |
| `DRY_RUN` | `true` | `false` |
Which environment a run uses is decided by the `x-fastn-env` header or the trigger route. See [Environments](/manage/environments.md).
---
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