Patent vs Trade Secret: Which Strategy for a Deeptech Start-up?

By Maître Arnaud Touati
06/10/2026

Reviewed and approved by Arnaud Touati (Maître), partner and co-founder of the firm

Key points

The choice between a patent and a trade secret turns on one question: is the technology vulnerable to reverse engineering? If so, the patent becomes the most suitable tool to preserve exclusivity.
A patent confers an exclusive right of exploitation for a maximum of 20 years in exchange for public disclosure, subject to three cumulative conditions under Article L. 611-10 of the French Intellectual Property Code (CPI): novelty, inventive step and industrial application.
The patent has one major weakness: the application is published 18 months after filing or priority, and its cost rises sharply with international extensions.
Trade secrets, codified in Articles L. 151-1 et seq. of the French Commercial Code (Code de commerce) since the law of 30 July 2018, protect information that is not known, has commercial value and is subject to reasonable measures.
A trade secret offers unlimited duration and low cost but protects neither against independent invention nor against reverse engineering, both lawful means of obtaining it under Article L. 151-3 of the Commercial Code, unless otherwise agreed by contract.
For most deeptech start-ups, a hybrid strategy is the way forward: patent the visible core and keep the industrialisation know-how secret.

The choice between a patent and a trade secret turns on a simple equation: is the technology vulnerable to reverse engineering? If so, the patent is the most suitable tool to avoid losing all exclusivity as soon as the product reaches the market. If not (internal process, cloud algorithm, chemical formulation that cannot be decoded), a trade secret can offer lasting, unlimited protection with no public disclosure. For most deeptech start-ups, a hybrid strategy is the way forward: patent the visible core, keep the industrialisation know-how secret.

Table of Contents

The patent: a limited monopoly in exchange for public disclosure

In France, patents are governed by Book VI of the French Intellectual Property Code. A patent confers on its owner an exclusive right of exploitation for a maximum of 20 years from filing (Article L. 611-2 of the CPI (in French)), in return for public disclosure of the invention.

What can be patented in France?

Article L. 611-10 of the Intellectual Property Code (in French) requires three cumulative criteria:

Novelty: the invention was not publicly disclosed before filing.
Inventive step: the invention is not obvious to a person skilled in the art, having regard to the state of the art.
Industrial application: the invention can be made or used in any kind of industry.

The following, in particular, are not regarded as inventions: discoveries, scientific theories and mathematical methods, methods for doing business and computer programs, but only as such (an invention involving software and producing a technical effect remains patentable, according to the case law of the European Patent Office).

Strengths of a patent

A monopoly enforceable against everyone, including a competitor who invented independently.
Civil and criminal infringement actions.
Direct value in fundraising (deeptech investors look at the patent portfolio).
Ability to license or assign, a source of revenue independent of exploitation.
A signalling effect for industrial partnerships and public procurement.

Weaknesses of a patent

Publication of the application after 18 months from filing or priority: the full description becomes available to any competitor.
Substantial cost: drafting and filing fees, then rising costs with international extensions (PCT procedure, European validations country by country).
Duration limited to 20 years, after which the invention falls into the public domain.
Lengthy examination: several years may pass before grant.
Difficulty proving infringement for processes or server-side algorithms where use of the patent is not visible.

Trade secrets: lasting but conditional protection

The trade secrets regime is codified in Articles L. 151-1 et seq. of the French Commercial Code (in French), since Law No. 2018-670 of 30 July 2018 (in French) transposing Directive (EU) 2016/943.

When is a trade secret protected under French law?

Article L. 151-1 of the Commercial Code (in French) requires three cumulative criteria:

Information that is not generally known or readily accessible.
Commercial value, actual or potential, because it is secret.
Reasonable protective measures taken by the holder.

Strengths of a trade secret

Unlimited duration as long as the three criteria are met.
No public disclosure: competitors learn nothing.
Low cost: investment in internal procedures, NDAs and IT security measures.
Immediate effect: no examination period.
Protection against complicit third parties: even a competitor who has not signed anything is liable if it knowingly exploited a misappropriated secret.

Weaknesses of a trade secret

No protection against independent invention: if a competitor invents the same thing on its own, it can exploit it and even patent it.
No protection against lawful reverse engineering: Article L. 151-3 of the Commercial Code (in French) lists among the lawful means of obtaining a secret the observation, study, disassembly or testing of a product made available to the public or lawfully held, unless otherwise agreed by contract.
Permanent loss in the event of disclosure: a leak (press article, conference, employee departure) destroys the protection.
Heavy organisational constraints: security policy, systematic NDAs, document marking, restricted access.
Difficult to value: a secret is hardly visible to an investor, unlike a patent portfolio.

The decisive criterion: vulnerability to reverse engineering

Can the technology be decoded once the product is on the market?

Yes, vulnerable: mechanical device, simple chemical formulation, visible client-side algorithm. → A patent is needed, otherwise the secret is lost immediately after market launch.
No, opaque: internal manufacturing process, complex formulation that cannot be decoded by analysis, server-side algorithm. → A trade secret remains viable.
Partly: part of the technology is visible, part is not. → Hybrid strategy.

The hybrid strategy: the most common practice

Most deeptech start-ups combine the two regimes:

Patents on visible, critical elements: product structure, core technical principle, method of use at the customer’s site.
Secrecy over manufacturing know-how: precise production parameters, optimisation recipes, training data, tool configuration.
Secrecy over usage data: customer feedback, continuous improvement data, internal benchmarks.

This split optimises value while preserving the industrial lead.

Artificial intelligence: patent or trade secret?

For an AI start-up, the strategy often leans towards secrecy:

Model weights are generally not patentable (they are the result of training, not an invention in the technical sense).
Training data can be protected by trade secrets and by the sui generis database right.
Training algorithms can be patented if they produce a technical effect beyond computation, but examination remains strict at the INPI (French patent office) and the EPO.
Specific hardware architectures (dedicated chips, training infrastructure) remain largely patentable.

Timing: file before any disclosure

The novelty required for a patent is absolute and assessed at the filing date: any prior disclosure (scientific article, trade fair presentation, customer demo, LinkedIn post) destroys patentability, even if it comes from the inventor.

Practical consequence: file before any public communication. French law has no general grace period comparable to that of certain countries such as the United States: Article L. 611-13 of the CPI disregards a disclosure made in the six months before filing only in the event of evident abuse or presentation at an official exhibition.

Common pitfalls

Premature disclosure: pitching to an investor without an NDA, an academic conference, entering a competition without a confidentiality clause. Novelty is lost.
Patent too broad: excessive claims that will be rejected on examination or invalidated in litigation.
Patent too narrow: claims easy to design around through a minor change to the competing product.
Secret without reasonable protective measures: no NDA, no marking, no access management. The regime does not apply because the third criterion is missing.
Underestimating international costs: protection in many countries via the PCT and national validations represents a significant budget, to be planned from the first filing.
Confusing software copyright with patents: source code is protected by copyright (with no formalities), not by patent in France.

The choice between patent and trade secret is made at the start of R&D, with an intellectual property lawyer. A poor initial strategy is almost impossible to correct later. Every situation is different and calls for a case-by-case analysis.