FDTDX
FDTDX: A free, code-driven FDTD library for GPU-based electromagnetic simulation and optimization. Ranked #20 of 89 in Physics Simulation Software by our editors (7.1/10); pricing: Free plan; best for researchers running GPU electromagnetic FDTD studies.
At a glance
- Editor score7.1 / 10
- PricingFree plan
- Best forResearchers running GPU electromagnetic FDTD studies
- Free planYes
- Paid fromFree
- Delivery modeDesktop
- Facts checked23 Sep 2026
Where it wins
- GPU acceleration and multi-GPU scaling for FDTD simulations
- Automatic differentiation supports gradient-based optimization
- Exports simulation arrays, JSON objects and 3D voxel geometry
Where it doesn't
- Requires a programmatic Python workflow
- Self-hosted use means users manage their own environment
- Its focus is FDTD simulation and photonic nanostructures
Our verdict on FDTDX
FDTDX is an open-source Python package for simulating and designing three-dimensional photonic nanostructures with the Finite-Difference Time-Domain method. It is aimed at researchers, engineers and developers working in computational electromagnetics and photonics, particularly those who want to define simulations in code and use GPU resources. Its emphasis is on programmable modeling and optimization rather than a hosted educational simulation experience, so it suits technical teams comfortable working through a Python API.
The package brings together GPU-accelerated FDTD, multi-GPU scaling and automatic differentiation for gradient-based optimization. Time-reversibility supports memory-efficient gradient computation. Users define materials and objects programmatically, then configure sources, detectors and boundary conditions. That combination is relevant when a study needs repeated simulation and parameter optimization, rather than only a single forward run. The published documentation includes quickstarts, physics tutorials and API references, which provide a route into the library, but the overall workflow remains code-led and self-hosted.
FDTDX is available as free, open-source software, with installation through pip. Its visualization and export options help connect simulation work to other workflows: it can visualize three-dimensional electromagnetic fields, export simulation arrays to VTI files, serialize objects to JSON, and export voxel geometry to STL. Choose it if GPU-based FDTD and programmable optimization are central to your photonics work and you can operate a Python-based environment. A researcher seeking a ready-made hosted interface or a general-purpose simulation product should look elsewhere; FDTDX's value is concentrated in its specialized, developer-oriented workflow.
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FDTDX pricing
FDTDX fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Delivery mode | Desktop |
| Lesson library | No |
| Authoring tools | Yes |
| Assessment tools | No |
| 3D visuals | Yes |
| Offline access | Not verified |
| Data export | Yes |
| Deployment | Self-hosted |
| Support | Docs |
| Built for | Solo, Small business, Mid-market, Enterprise (editorial estimate) |
| Pricing | Free plan |
| Website | fdtdx.readthedocs.io |
| Facts checked | 23 Sep 2026 |
Alternatives to FDTDX
- COMSOL MultiphysicsA broad desktop environment for coupled physics, engineering models, and custom simulation apps.9.4
- Ansys FluentA deep CFD and HPC environment for demanding industrial simulation work.9.3
- SimScaleA broad browser-based multiphysics platform with flexible cloud workflows and tiered access.9.1
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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