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AI · head to head

Aider vs Sigil

A

Aider

AI

AI pair programming in your terminal

From
Free
Rated
-
Full reviewWebsite
Sigil logo

Sigil

Publishing

Open source EPUB editor for working directly on the file, not generating it

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Aider requires comfort working in a terminal rather than a graphical IDE; Sigil it produces no print output whatever, so any book that needs a paperback interior requires a completely separate tool and a second workflow.
  • They diverge on capability: Aider covers Multi-LLM support, Sigil covers Direct EPUB editing.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Aider and Sigil actually diverge.

Attributes where Aider and Sigil differ
AttributeAiderSigil
Pricing modelopen-sourceOpen source, no licence fee
Platformsmac, linux, windows, apiWindows, macOS, Linux
CategoryAIPublishing
Founded2023Unknown

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Aider

  • Multi-LLM support
  • Repository mapping
  • Git integration
  • Voice-to-code
  • Lint and test automation
  • Image and web context
  • Free provider access
  • Editor file-watching

Only in Sigil

  • Direct EPUB editing
  • Code and preview views
  • EPUB 2 and EPUB 3
  • Regex across files
  • Validation
  • Python plugins

What people use each for

The jobs each tool is most often brought in to do.

Aider

  • Editing an existing codebase from the terminalnot Sigil
  • Pairing with an LLM on a new projectnot Sigil
  • Automating git-committed code changesnot Sigil
  • Working across many programming languagesnot Sigil
  • Bringing your own LLM API key to a coding workflownot Sigil

Sigil

  • Fixing an EPUB that a retailer validator has rejected, without re-exporting from the tool that generated itnot Aider
  • Correcting the table of contents, reading order or metadata in a file supplied by a conversion servicenot Aider
  • Preparing a back-catalogue title where the only surviving source is the EPUB itselfnot Aider
  • Applying a consistent stylesheet or a bulk text correction across every chapter of a book at oncenot Aider

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Aider

  • Requires comfort working in a terminal rather than a graphical IDE
  • Has no hosted or managed version, so users must supply and pay for their own LLM API access separately
  • Depends heavily on the chosen underlying model's quality, so results vary by which LLM is configured
  • Lacks a built-in autonomous multi-step task runner comparable to agent-style products

Sigil

  • It produces no print output whatever, so any book that needs a paperback interior requires a completely separate tool and a second workflow.
  • Meaningful use requires reading and writing HTML and CSS, which puts it out of reach of most authors who simply want a finished file.
  • There is no cloud storage, sync or collaboration, so the book exists as a file on one machine and version control is whatever you set up yourself.
  • Development depends on a small number of volunteer maintainers, so release timing and platform builds follow their availability rather than a roadmap, and a lapse in maintenance would leave no obvious successor.
  • It provides no distribution, no retailer connection and no Kindle-native output, so it sits in the middle of a workflow that other tools have to complete on both sides.

Pricing, plan by plan

Aider

Free

No published plan breakdown. See the Aider review.

Sigil

Free
  • SigilFree
    • GPL licensed with no cost or account required
    • Full functionality with no feature gating
    • Community support through forums and the issue tracker

Which should you pick?

Choose Aider if

  • You need multi-llm support.
  • You want to start without paying.
  • You work on mac, linux, windows, api.
  • You also want repository mapping.
Aider review

Choose Sigil if

  • You need direct epub editing.
  • You want to start without paying.
  • You work on Windows, macOS, Linux.
  • You also want code and preview views.
Sigil review

Questions people ask

Is Aider or Sigil better?
Neither clearly leads. Aider starts at Free and Sigil at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Aider or Sigil?
Aider starts at Free and Sigil at Free.
Does Aider or Sigil run on more platforms?
Aider runs on mac, linux, windows, api. Sigil runs on Windows, macOS, Linux.
Can I use Aider for free?
Both have a free tier, so you can try either at no cost before committing.
What is Aider best used for?
Aider is most often used for editing an existing codebase from the terminal, pairing with an llm on a new project, automating git-committed code changes, working across many programming languages. Of those, editing an existing codebase from the terminal and pairing with an llm on a new project are not what Sigil is typically brought in for.
What can Aider do that Sigil cannot?
Aider covers Multi-LLM support, Repository mapping, Git integration, Voice-to-code. Sigil covers Direct EPUB editing, Code and preview views, EPUB 2 and EPUB 3, Regex across files.

Answered from the vendors’ own pages

Aider: Is Aider free to use?

Aider itself is free and open source, released under the Apache 2.0 license. Users must separately supply and pay for API access to the LLM they choose to use with it.

Source
Sigil: Can I write my book in Sigil?

You can, but you should not. It is an EPUB editor, not a word processor, and writing long-form prose in it is unpleasant. Write elsewhere, import, then finish in Sigil.

Aider: Which LLMs can I use with Aider?

Aider connects to OpenAI, Anthropic, Gemini, GROQ, DeepSeek, Ollama, Azure, Cohere, xAI, GitHub Copilot, Vertex AI, Amazon Bedrock, OpenRouter and most other LLM providers via API keys.

Source
Sigil: Does it make Kindle files?

Not natively. Produce a valid EPUB in Sigil and let Amazon convert it, or use a separate conversion tool for other Kindle formats.

Aider: Can I use Aider for free without paying for an LLM API?

Yes, Aider can be used at no cost through OpenRouter's free model access (subject to daily usage limits) or Google's Gemini 2.5 Pro Exp, which the docs note performs well without a paid API key.

Source
Sigil: Is it safe to rely on a volunteer project for commercial work?

The files it produces are standard EPUB, so nothing is locked in. The risk is that maintenance stops, not that your books become unreadable.

Aider: How does Aider handle version control?

Aider automatically stages and commits each change it makes to a connected git repository, generating a descriptive commit message for every edit so changes stay reviewable and reversible.

Source
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