# Environment variables¶

Here are the environment variables Chainer uses.

 CHAINER_CUDNN Set 0 to disable cuDNN in Chainer. Otherwise cuDNN is enabled automatically. CHAINER_SEED Default seed value of random number generators for CUDA. If it is not set, the seed value is generated from Python random module. Set an integer value in decimal format. CHAINER_TYPE_CHECK Set 0 to disable type checking. Otherwise type checking is enabled automatically. See Type checking utilities for details. CHAINER_DEBUG Set 1 to enable debug mode. It is disabled by default. In debug mode, Chainer performs various runtime checks that can help debug user’s code at the cost of some overhead. For details, see Debug mode.