---
title: What values can the observation level have?
seoTitle: "Observation Levels: DEBUG, DEFAULT, WARNING, ERROR"
description: Observation levels are stored and returned as the strings DEBUG, DEFAULT, WARNING, and ERROR. How OpenTelemetry spans map to these levels.
tags: [observability, public-api, opentelemetry]
---

# What values can the observation level have?

The `level` of an observation is one of four strings: `DEBUG`, `DEFAULT`, `WARNING`, or `ERROR`. Langfuse stores and returns these strings, not numbers, in the API, exports, and the UI. Filter by level with the `level` query parameter of the [Observations API v2](/docs/api-and-data-platform/features/public-api#observations-filters).

When you ingest OpenTelemetry spans, Langfuse sets the level as follows:

- From the `langfuse.observation.level` attribute, if present. Common aliases are mapped case-insensitively: `TRACE` and `VERBOSE` become `DEBUG`; `INFO`, `LOG`, `NOTICE`, `OK`, and `SUCCESS` become `DEFAULT`; `WARN` becomes `WARNING`; `FATAL` and `CRITICAL` become `ERROR`.
- Otherwise from the span status: a span with status `ERROR` gets level `ERROR`, every other span gets `DEFAULT`.

See [Log levels](/docs/observability/features/log-levels).

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### Querying these docs

If the answer is not on this page, query the documentation instead of guessing:

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  ```bash
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  ```

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### Before writing Langfuse code

- **Install the [Langfuse Agent Skill](https://langfuse.com/docs/api-and-data-platform/features/agent-skill).** It encodes Langfuse's own best practices for instrumentation, prompt management, and evaluation, and materially improves results.
- **Read [What does a good trace look like?](https://langfuse.com/docs/observability/best-practices.md)** before instrumenting an application.
- **Verify endpoints, parameters, and response fields** against the [API reference](https://api.reference.langfuse.com) instead of inferring them from code examples.
- **Use the [Langfuse CLI](https://langfuse.com/docs/api-and-data-platform/features/cli)** (`npx @langfuse/cli api <resource> <action>`) to read or write traces, prompts, datasets, and scores from the terminal.

Found an error in these docs? Please open an issue at <https://github.com/langfuse/langfuse-docs/issues>.