Use cases
Alternative to the Soleau Envelope and e-Soleau
The paper Soleau envelope was replaced in 2020 by INPI's e-Soleau, still active at €15 for 5 years. Proxae is a complementary alternative — free, instant, and permanent, anchored in the Bitcoin blockchain.
Soleau, e-Soleau: where things stand in 2026
The paper Soleau envelope was created in 1910 by France's National Institute of Industrial Property (INPI). For over a century, it allowed French inventors, designers, and creators to prove the prior existence of their creations at low cost.
In 2020, INPI discontinued the paper Soleau envelope and replaced it with e-Soleau, a fully online service. e-Soleau is still active today: it costs €15 per deposit and stores files for 5 years, renewable once (15 years maximum).
e-Soleau remains an official French tool, well-established, with decades of case law behind the Soleau envelope concept.
Some practical limitations of e-Soleau:
- ▸ INPI receives and stores your file (no full confidentiality)
- ▸ Accepted formats are limited (mainly PDF)
- ▸ Storage duration capped at 5-15 years
- ▸ Primarily a French mechanism
- ▸ €15 per deposit, every time
Proxae — what's different?
Absolute confidentiality
The SHA-256 hash is computed in your browser — your content never leaves your device.
Blockchain anchoring
Each proof is anchored in the Bitcoin blockchain via OpenTimestamps, the open standard for decentralized timestamping.
Permanent validity
No renewal, no expiration. The proof exists as long as the Bitcoin blockchain exists.
Verifiable by anyone
Anyone can verify a Proxae proof independently, without relying on any central authority.
All formats accepted
PDF, images, source code, ZIP archives, videos — any file up to 50 MB.
Free or Pro
Free unlimited use, or Pro at €4.90/month with eIDAS-qualified timestamping (RFC 3161 Sectigo) recognized across the EU.
Detailed comparison: Soleau vs Proxae
| Soleau Envelope (paper, 1910-2020) | e-Soleau (INPI, since 2020) | Proxae Free | Proxae Pro | |
|---|---|---|---|---|
| Status in 2026 | Discontinued | Active | Active | Active |
| Cost | — | €15 per deposit | Free, unlimited | €4.90/month |
| Format | 7 A4 paper pages | Limited PDF | All formats up to 50 MB | All formats up to 50 MB |
| Validity period | — | 5 years renewable (max 15 years) | Lifetime | Lifetime |
| Third-party verifiable | INPI only | INPI only | Publicly (Bitcoin) | Publicly + eIDAS qualified |
| Confidentiality | INPI paper archive | INPI receives the file | No content transmitted | No content transmitted |
| Speed | Several days | A few minutes | 30 seconds | 30 seconds |
| Geographic scope | France | France | Worldwide | Worldwide + EU eIDAS |
| Renewal | — | Every 5 years | Never | Never |
When e-Soleau is enough
e-Soleau is an official tool that works well in certain contexts:
- ✓ You're making a one-time, single deposit
- ✓ You're operating within the French legal framework
- ✓ Your document is a short PDF that fits e-Soleau's limits
- ✓ You're comfortable with the cost (€15) and processing time
- ✓ You're willing to renew every 5 years
- ✓ You're okay sending your file to INPI
- ✓ You want an explicitly French institutional mechanism
When Proxae becomes more relevant
- ✦ You timestamp regularly (multiple files per month or year)
- ✦ Your files exceed e-Soleau's limits (size, format, type)
- ✦ You want proof that doesn't expire after 5-15 years
- ✦ You want proof that's verifiable without relying on any institution
- ✦ You need legal value recognized across the entire EU (Pro)
- ✦ You want your content to stay strictly on your device
- ✦ You operate internationally
Can you use both?
Yes — it's even recommended for strategic documents. Combining an e-Soleau deposit with a Proxae timestamp gives you two independent proof angles: a French institutional anchor and a global cryptographic anchor. In case of a dispute, multiple proofs strengthen your position.
See a concrete scenario
What actually happens when you need your proof in a dispute? Three realistic scenarios — designer, developer, author — show you the complete journey, from certification to legal use.
See dispute scenarios →Frequently asked questions
Does the Soleau envelope still exist?
Does e-Soleau have more legal value than Proxae?
What exactly is Proxae Pro with eIDAS?
Can you use Proxae alongside e-Soleau?
What happens if Proxae disappears in 10 years?
Is Proxae timestamping recognized in court?
A free, instant, and permanent alternative to the Soleau envelope.
Proxae provides cryptographic proof of prior existence. It does not confer exclusive rights and does not replace a notarized act or personalized legal advice. For any real dispute, consult a lawyer.