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Ellf by Explosion: build custom NLP models with your coding assistant, now free on one machine

Ellf, from Explosion (the makers of spaCy and Prodigy), plugs into coding assistants such as Claude Code, Codex or GitHub Copilot so they can build custom NLP models end to end: planning, annotation, training and evaluation. Its new Solo plan lets you use Ellf free on a single machine, with all features.

Last checked · Announced · By Mishal Brands Editorial

Checked Nov 10, 2026. Everything below is what the company reports in its own announcement, linked at the bottom: Explosion, “Introducing Ellf: The missing piece for building NLP with coding assistants” (Solo plan added Nov 2, 2026) (Oct 14, 2026). We have not tested it ourselves, and figures are the company’s own unless we say otherwise.

What it does and why it matters

Coding assistants are good at code but tend to skip the data work NLP needs: they cannot ask a human to label examples, are awkward for long-running jobs, and default to “just use an LLM.” Ellf fills those three gaps with annotation, execution and a knowledge base from Explosion’s 10+ years of applied NLP (Explosion, Oct 14, 2026).

Explosion’s example is support tickets: Ellf proposes a named entity recognizer for fields like product and error code, plus a text classifier for routing, then helps you annotate a few hundred examples and train a small model you own.

Who it is for

  • Developers replacing an expensive LLM API call with a small custom model.
  • Teams with privacy-sensitive or regulated data: computation runs on your own cluster.
  • Not for non-technical users: you work through a coding assistant and a CLI.

Standout features

  • Works with your assistant: Claude Code, Codex, GitHub Copilot and others.
  • Annotation built in with Prodigy, plus LLM-powered auto-annotation agents that draft labels for humans to review.
  • Your compute: a Kubernetes cluster in your cloud or on your machine; Explosion says your data is never sent to it.
  • Recipes, tasks, actions, agents and services as Python functions with a web form and matching CLI.
  • Project templates, including the support-ticket example and LLM pipeline evaluation.

How to start

  1. Sign up, install the Ellf CLI and connect it to your coding assistant.
  2. Set up a cluster; on the Solo plan it runs on your local machine.
  3. Describe your goal to your assistant and let Ellf write a project plan.
  4. Annotate a few hundred examples, train, and compare against your current approach.

Alternatives

  • Claude or ChatGPT through an API, if a general LLM is accurate and cheap enough.
  • Cursor as the coding assistant that drives the work.

Frequently asked questions

What is Ellf?

A tool from Explosion that plugs into your coding assistant and gives it what it needs to build custom NLP systems: annotation, execution on your own cluster, and NLP know-how.

Does my data leave my machine?

Explosion says computation runs on a cluster you control and your data is never sent to it; its servers never make requests to your cluster.

Is Ellf free?

Explosion says the new Solo plan lets you use Ellf for free on a single machine with all features and coding-agent integration. Other plans start with a free trial.

Pricing and free plan for Ellf

Explosion says the Solo plan is free on a single machine and includes all features and coding agent integration, with a data-private cluster on your local machine. For team use, its announcement points to a free trial; see our Ellf page for the plan facts we checked.

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Sources (checked Nov 10, 2026)

Disclosure: this page has no affiliate links. No company paid for or reviewed it. See our affiliate disclosure and how we review.

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