# Environment variables

Boolean variables accept `1`, `on`, `yes`, or `true` in any capitalization. Anything else, including unset, is false.

Most of these variables are read once, when Transformers is imported. Set them in your shell before launching Python, or with [os.environ](https://docs.python.org/3/library/os.html#os.environ) before the import. Changing them afterwards has no effect.

```bash
TRANSFORMERS_VERBOSITY=info python run.py
```

Caching and Hub access are configured by the `HF_*` variables [huggingface_hub](https://huggingface.co/docs/huggingface_hub/package_reference/environment_variables) owns, such as `HF_HOME` and `HF_HUB_OFFLINE`. See [Installation](../installation#offline-mode) for the offline workflow.

## Logging

Transformers logs at `warning`. [Logging](../main_classes/logging) documents the equivalent Python API, including [logging.set_verbosity()](/docs/transformers/v5.17.0/en/main_classes/logging#transformers.utils.logging.set_verbosity).

| Variable | Values | Description |
|---|---|---|
| `TRANSFORMERS_VERBOSITY` | `detail`, `debug`, `info`, `warning`, `error`, `critical` | Library log level. `detail` matches `debug` and adds the filename and line number to each message. An unrecognized value warns and falls back to `warning`. |
| `TRANSFORMERS_NO_ADVISORY_WARNINGS` | boolean | Silences advisory warnings, the best-practice hints that don't indicate a problem. |

## Model loading

Checkpoint shards load in parallel by default.

| Variable | Values | Description |
|---|---|---|
| `HF_DEACTIVATE_ASYNC_LOAD` | boolean | Loads shards on the main thread instead of a thread pool. Slower, but peak memory is easier to reason about. Loading is already sequential when a `device_map` offloads to disk or when quantizing on the fly, so this only affects otherwise parallel loads. |
| `DISABLE_SAFETENSORS_CONVERSION` | boolean | Stops Transformers from asking the Hub conversion bot for a safetensors version of a repository that ships only PyTorch `.bin` weights. Worth setting in CI, where the request adds latency and network flakiness. |

## Kernels and backends

Optimized kernels are downloaded from the Hub when [kernels](https://github.com/huggingface/kernels) is installed and the hardware supports them. Disable them to isolate a numerical difference or a crash.

| Variable | Values | Description |
|---|---|---|
| `USE_HUB_KERNELS` | boolean, enabled by default | Set to a false value to fall back to the reference implementations. |
| `TRANSFORMERS_DISABLE_DEEPGEMM_LINEAR` | `1` | Forces the Triton fallback instead of DeepGEMM for FP8 linear layers in finegrained FP8 quantization. |
| `TRANSFORMERS_DISABLE_TORCH_CHECK` | `1` | Skips the minimum PyTorch version check at import. |

> [!WARNING]
> `TRANSFORMERS_DISABLE_TORCH_CHECK` removes a guard rather than changing behavior. On an unsupported PyTorch version you get import errors or silently wrong results instead of a clear message.