synax simulates Galactic synchrotron emission, covering both total and polarized intensity. It leverages the power of JAX (ascl:2111.002), and provides automatic differentiation (AD) and multi-platform support (CPU, GPU, TPU), among other features. By providing gradient access, synax integrates smoothly into the JAX ecosystem, enabling the use of efficient inference algorithms, including Hamiltonian Monte Carlo (HMC) and ADAM optimization.