How to Share Large Files Securely

Sending a multi-gigabyte file to a colleague, client, or partner has become an everyday task. But between email attachment size limits, transfer services that expose your data, and enterprise solutions too complex to deploy, finding the right tool often feels like an obstacle course. This practical guide shows you how to share large files securely, step by step, without compromising data confidentiality.

The large file problem in 2026

The average size of files exchanged in business continues to grow. 4K presentation videos, 3D architectural models, analytics datasets, project backups: requirements regularly exceed the gigabyte mark. Yet traditional communication channels were never designed for these volumes.

Email remains limited to 25 MB with most providers (Gmail, Outlook, etc.). Instant messaging platforms like Slack or Teams impose similar restrictions. That leaves file transfer services, but not all are equal when it comes to security and capacity.

Size limits compared: the available options

Here is an overview of the main file transfer solutions and their free-tier limits:

WeTransfer: up to 2 GB per transfer on the free plan. No end-to-end encryption. Files stored in clear text on servers. Hosted outside France.
Tresorit Send: up to 5 GB on the free plan. End-to-end encryption. Hosted in Europe (Switzerland). Professional interface, but advanced features reserved for paid subscriptions.
Internxt Send: up to 5 GB on the free plan. End-to-end encryption. Hosted in Europe. Open source.
ZeroTrustTransfer: up to 10 GB per transfer. AES-256-GCM end-to-end encryption. Zero-knowledge architecture. Hosted in France. From EUR 199 lifetime licence.

Transfer capacity is just one criterion among many. A service that accepts 10 GB but stores your files in clear text on American servers is less secure than one limited to 5 GB with genuine end-to-end encryption.

5 steps to a secure file transfer

Regardless of which service you choose, follow these five steps to ensure the security of your large file transfers:

Step 1: Choose a service with end-to-end encryption

This is the non-negotiable criterion. End-to-end encryption ensures that your files are unreadable to the service provider and to any attacker who might compromise its servers. Verify that encryption happens client-side, meaning in your browser or application, before upload. If the provider only mentions "encryption in transit" (TLS) or "encryption at rest", that is not end-to-end encryption.

Step 2: Enable password protection

If the service offers it, add a password to your transfer. This password creates an additional layer of protection: even if the download link is intercepted or accidentally shared, the file remains inaccessible without the password. Choose a strong password of at least 12 characters, combining letters, numbers, and special characters.

Step 3: Set an expiration date

Never leave a file accessible indefinitely. Configure an expiration date appropriate to the context: 24 hours for an urgent document, one week for an ongoing project, never more than a month. After this period, the file is automatically deleted, reducing the exposure window in case the link is compromised.

Step 4: Share the link securely

The download link is the key to your file. Transmit it through a secure channel and, crucially, never share the password in the same channel as the link. If you send the link by email, communicate the password via SMS or an encrypted messaging app. This channel separation is a golden rule of security.

Step 5: Verify the download

Confirm with your recipient that they have successfully received and downloaded the file. Some services offer download notifications that alert you when the file has been retrieved. Once download is confirmed, you can manually delete the transfer if the service allows it, rather than waiting for automatic expiration.

Tips to optimise your transfers

Beyond the five essential steps, a few additional best practices will help you gain efficiency and security:

Compress your files before sending: a ZIP or 7z file reduces transfer size and bundles multiple files into one. For very large files, compression can save 20-50% in volume depending on the content type.
Use password-protected archives: for an extra security layer, create an encrypted archive (7-Zip with AES-256) before uploading it to the transfer service. Even if the service is compromised, the archive remains encrypted.
Prefer single-use links: some services allow you to limit the number of downloads. A single-use link ensures that only one person can retrieve the file.
Avoid revealing filenames: a file named "contract-client-smith-confidential.pdf" gives away exploitable information before it is even opened. Use neutral or coded names instead.
Check metadata: Office and PDF files often contain metadata (author, organisation, revision history) that can reveal sensitive information. Clean them before sending.

The security of a file transfer does not depend solely on the tool you choose. It rests on a chain of best practices, from file preparation to download confirmation.

Common mistakes to avoid

Some widespread habits seriously compromise transfer security:

Sending the password in the same email as the link: this is the equivalent of sticking the safe code on the door. If the email is intercepted, the attacker has everything they need.
Using links that never expire: a permanent link is a permanent risk. It only takes someone finding it in an old email, a browser history, or an archived conversation thread.
Neglecting recipient verification: a typo in an email address can send your link to a stranger. Always double-check the recipient's address before sending.
Trusting TLS encryption alone: TLS protects data in transit between your browser and the server. Once on the server, your files are in clear text. That is not enough.

ZeroTrustTransfer: large and secure file transfers

ZeroTrustTransfer ticks every box for secure large file transfers. With capacity up to 10 GB per transfer, AES-256-GCM end-to-end encryption performed directly in your browser, and a zero-knowledge architecture, your files remain confidential from end to end.

Password protection is available as an option, automatic deletion is configurable, and hosting is entirely in France. All from EUR 199 as a lifetime licence, with no monthly subscription and no transfer limits.

Whether you need to send mockups to a client, financial data to an auditor, or medical records to a practitioner, ZeroTrustTransfer gives you the peace of mind of a transfer that is both large-capacity and genuinely secure.