Legal · head to head
Luminance vs Spellbook
Luminance
Legal
Machine learning contract analysis for review, negotiation and compliance
- From
- On request
- Rated
- -
Spellbook
Legal
Contract drafting and review assistant inside Microsoft Word
- From
- On request
- Rated
- -
The short version
- Each has a real cost: Luminance no independent evaluation of its accuracy has been published, and it did not take part in the Vals Legal AI Report, so buyers have only vendor-produced evidence to work from.; Spellbook it publishes no accuracy figure for its own output and no independent evaluation exists, so a firm must run its own assessment on real agreements.
- They diverge on capability: Luminance covers Anomaly detection, Spellbook covers Word add-in drafting.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which Luminance and Spellbook actually diverge.
Identical on both: starting price (On request), pricing model (quote), free tier (No), user rating (Not yet rated), category (Legal).
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 Luminance
- Anomaly detection
- Contract negotiation
- Due diligence review
- Multi-language analysis
- Document comparison
Only in Spellbook
- Word add-in drafting
- Contract review
- Benchmarks against market standards
- Question answering
- Named model providers
What people use each for
The jobs each tool is most often brought in to do.
Luminance
- In-house teams auditing a contract estate for a specific exposure such as change of controlnot Spellbook
- Procurement and compliance functions reviewing supplier agreements at scalenot Spellbook
- Transaction teams reviewing large contract populations against a deal deadlinenot Spellbook
- Negotiation teams applying a standard playbook consistently across many counterpartiesnot Spellbook
Spellbook
- Transactional lawyers drafting commercial agreements in Wordnot Luminance
- In-house teams reviewing inbound contracts without a contract lifecycle systemnot Luminance
- Lawyers who want a first pass at redlines before applying their own judgementnot Luminance
- Firms that need to know which model providers process their documents before adopting an AI toolnot Luminance
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
Luminance
- No independent evaluation of its accuracy has been published, and it did not take part in the Vals Legal AI Report, so buyers have only vendor-produced evidence to work from.
- The one named accuracy benchmark, ContractIQ Bench, was built, run and scored by Luminance on a dataset it has not released, against comparison models it does not name.
- Value scales with document volume, so an organisation reviewing tens rather than thousands of contracts will not recover the licence cost.
- Output still requires qualified review, so it reduces reading time rather than removing the lawyer, and staffing plans that assume otherwise fail.
- Pricing is not published, so cost per matter cannot be modelled until after a sales process and a proof of concept.
Spellbook
- It publishes no accuracy figure for its own output and no independent evaluation exists, so a firm must run its own assessment on real agreements.
- The ten times more accurate claim originated in a funding announcement as a statement of intent and has no methodology, dataset or baseline behind it.
- Contract text is processed by third-party model providers, so despite the zero data retention agreements this still needs checking against client confidentiality terms and outside counsel guidelines.
- Pricing is not published, so seat cost cannot be compared against competitors without booking a demo.
- It is a drafting assistant rather than a contract lifecycle system, so it does nothing for execution, obligation tracking or renewals.
Pricing, plan by plan
Luminance
On request- Luminance$undefined/year
- Enterprise licensing quoted per organisation
- Scoped by user count and document volume
- Proof of concept normally run before contracting
Spellbook
On request- Spellbook$undefined/year
- Priced by the number of seats on the licence
- Rates quoted after a demo, not published
- Seven day free trial, free access for academic use
Which should you pick?
Choose Luminance if
- You need anomaly detection.
- You work on Web, Windows.
- You also want contract negotiation.
Choose Spellbook if
- You need word add-in drafting.
- You work on Windows, macOS, Web.
- You also want contract review.
Questions people ask
- Is Luminance or Spellbook better?
- Neither clearly leads. Luminance starts at On request and Spellbook at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Luminance or Spellbook?
- Luminance starts at On request and Spellbook at On request.
- Does Luminance or Spellbook run on more platforms?
- Luminance runs on Web, Windows. Spellbook runs on Windows, macOS, Web.
- What is Luminance best used for?
- Luminance is most often used for in-house teams auditing a contract estate for a specific exposure such as change of control, procurement and compliance functions reviewing supplier agreements at scale, transaction teams reviewing large contract populations against a deal deadline, negotiation teams applying a standard playbook consistently across many counterparties. Of those, in-house teams auditing a contract estate for a specific exposure such as change of control and procurement and compliance functions reviewing supplier agreements at scale are not what Spellbook is typically brought in for.
- What can Luminance do that Spellbook cannot?
- Luminance covers Anomaly detection, Contract negotiation, Due diligence review, Multi-language analysis. Spellbook covers Word add-in drafting, Contract review, Benchmarks against market standards, Question answering.
Answered from the vendors’ own pages
Luminance: Is Luminance's accuracy independently verified?
No independent verification has been published. It did not participate in the Vals Legal AI Report, the main lawyer-baselined benchmark, and the only named benchmark in its materials is one it built and ran itself. Treat the published figures as vendor claims and run a proof of concept on your own documents.
Spellbook: Is Spellbook's accuracy independently verified?
No. It publishes no accuracy figure of its own, and no third-party evaluation has been published. It did not participate in the Vals Legal AI Report, the main independent lawyer-baselined benchmark. Evaluate it on your own agreements during the trial.
Luminance: What do the ninety per cent time-saving claims mean?
They are unattributed marketing figures about time and cost rather than accuracy, published without methodology, dataset or baseline. They are not a measure of how often the software is right.
Spellbook: Which models does it use and where does our text go?
Spellbook names OpenAI GPT-5 and Anthropic Claude models, and states it has zero data retention agreements with both providers. Confirm the current terms and subprocessor list against your client confidentiality obligations before use.
Luminance: Who backs Luminance?
It launched in 2016 with backing from Invoke Capital, the fund founded by Mike Lynch, and has since raised further rounds led by March Capital and Point72 Private Investments.
Spellbook: What does it cost?
Pricing is per seat but is not published. The vendor quotes it after a demo, so the seat rate cannot be compared with competitors in advance.
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