# Twinworks > Model a production line, simulate it and find the bottleneck — free, in your browser. Twinworks is a factory digital twin that runs entirely in your browser. Draw a production line on a floor plan with sources, buffers, machines, assembly stations, conveyors, quality checks and operators, then watch a seeded discrete-event simulation animate it in 2D or 3D. Live KPIs show throughput, lead time, WIP with a Little’s-law check, OEE per machine, state Gantt charts and the bottleneck, and the scenario manager, parameter sweeps and cost model turn it into a what-if laboratory. Twinworks (Factory digital twin & production simulation) is a premium app of usefulweb.site (https://usefulweb.site/): a full program that runs in the browser. Its engine is deterministic and the same functions are exposed as tools, so an agent can compute exactly what the app shows. ## Use it - Landing page: https://twinworks.usefulweb.site/ - Workspace (browser app): https://twinworks.usefulweb.site/app - open a project with https://twinworks.usefulweb.site/app#project= or a template with https://twinworks.usefulweb.site/app#template= - Project file format (JSON Schema): https://twinworks.usefulweb.site/project.schema.json - Tutorials: https://twinworks.usefulweb.site/tutorials - JSON API: POST https://twinworks.usefulweb.site/api/v1/tools//calculate (catalog: https://twinworks.usefulweb.site/api/v1/tools) - OpenAPI: https://twinworks.usefulweb.site/openapi.json - MCP (Streamable HTTP): https://twinworks.usefulweb.site/mcp ## Engine tools - [Twinworks Factory Simulation](https://twinworkssimulate.usefulweb.site/): Simulate a production line: throughput, lead time, WIP, OEE and the bottleneck, with CIs. API: POST https://twinworks.usefulweb.site/api/v1/tools/twinworks-simulate/calculate · MCP tool `twinworks_simulate` - [Twinworks Bottleneck Analysis](https://twinworksbottleneckanalysis.usefulweb.site/): Find the constraint of a production line and test fixes: ranked bottlenecks with what-if gains. API: POST https://twinworks.usefulweb.site/api/v1/tools/twinworks-bottleneck-analysis/calculate · MCP tool `twinworks_bottleneck_analysis` - [Twinworks Line Balancing](https://twinworkslinebalance.usefulweb.site/): Assign assembly tasks to stations for a takt time: efficiency, balance delay and smoothness index. API: POST https://twinworks.usefulweb.site/api/v1/tools/twinworks-line-balance/calculate · MCP tool `twinworks_line_balance` - [Twinworks Buffer & Parameter Sweep](https://twinworksbuffersweep.usefulweb.site/): Sweep a buffer size (or any parameter) and get the throughput curve with confidence intervals. API: POST https://twinworks.usefulweb.site/api/v1/tools/twinworks-buffer-sweep/calculate · MCP tool `twinworks_buffer_sweep` - [Twinworks Queueing Check](https://twinworksqueueformulas.usefulweb.site/): M/M/1, M/M/c, M/D/1, M/G/1 and Kingman waiting times — optionally verified by simulation. API: POST https://twinworks.usefulweb.site/api/v1/tools/twinworks-queue-formulas/calculate · MCP tool `twinworks_queue_formulas` ## Formats - Import: Twinworks project (.twinworks.json), Twinworks model JSON, Project link (#project=…) - Export: Twinworks project (.twinworks.json), CSV event log, CSV time series, CSV station KPIs, PNG and SVG of the layout, PNG and SVG of charts, Printable KPI report (PDF via print) ## Limits - Discrete parts only: no continuous flow (liquids, bulk material) or fluid tanks. - Transport between objects is instantaneous unless you model it as a conveyor; there are no AGVs, forklifts or path finding. - Operators are pooled resources without walking times, skills matrices or individual schedules. - Conveyors use a slot model (length ÷ pitch) rather than exact physics; merges and curves are not modelled geometrically. - The 3D view is a schematic visualisation, not CAD; no import of 3D models or DWG floor plans. - No optimisation solver: sweeps change one parameter at a time. - API calls are limited to roughly 40 million events per request; long studies run best in the app.