Browser vs Server: WhatsApp Export Processing

When you upload a WhatsApp export to WaChat to PDF, the conversion can happen in one of two fundamentally different ways. Browser mode runs the entire process inside your web browser, keeping your data entirely on your own device. Server mode sends the file to WaChat to PDF's secure processing infrastructure, where a more powerful environment handles the conversion in the background. Both modes produce a high-quality PDF, but they differ significantly in privacy characteristics, file size limits, and available features.

Browser Mode - How It Works

In browser mode, the JavaScript code running in your browser tab does all the work. The ZIP file you select is read directly from your local drive into browser memory - it is never sent over the network. The parser extracts and processes the _chat.txt and media files entirely within the browser sandbox, generates the PDF layout, and produces the output file in memory before offering it as a download. Your WhatsApp data never leaves your device.

This approach uses Web Workers to offload the heavy computation off the browser's main thread, which keeps the interface responsive during processing. For exports up to roughly 200–300 MB, browser mode is fast and seamless on most modern devices. Larger files work but become progressively slower as the browser allocates more memory to hold the ZIP contents, parsed messages, and the PDF being constructed simultaneously.

Server Mode - How It Works

In server mode, you upload the ZIP file to WaChat to PDF's secure storage, where it is placed in a processing queue. A dedicated worker server picks up the job and runs through a series of processing phases: downloading your file, extracting it, parsing the chat, processing media, building the layout, applying any redactions or Bates numbers, rendering the PDF using a headless browser, and encrypting the result before uploading it back to secure storage.

The entire server-side pipeline is designed for reliability with large files. Because it runs on dedicated infrastructure rather than in a browser tab, it is not constrained by device RAM or browser memory limits. You can close your browser after uploading - the job continues in the background. When complete, you receive a link to download the encrypted, integrity-hashed PDF output. See <a href='/how-it-works'>how WaChat to PDF processing works</a> for the full technical breakdown.

Privacy Comparison

Browser mode provides the highest possible privacy guarantee: your WhatsApp data never leaves your device and is never transmitted over any network. There is no upload, no server processing, no third-party storage, and no log of your export. For users with highly sensitive conversations - anything legally privileged, personally sensitive, or involving third parties who have not consented to sharing - browser mode eliminates the privacy surface entirely.

Server mode necessarily involves uploading your WhatsApp export to WaChat to PDF's servers. The service is designed with privacy in mind - uploads are encrypted in transit and at rest, processed files are deleted from servers within 24 hours of download, and no message content is read, logged, or used for any purpose other than producing the PDF. The full details are in the <a href='/privacy'>WaChat to PDF privacy policy</a>. For most users this level of protection is more than sufficient, but browser mode is the right choice when absolute data sovereignty is required.

Feature Comparison

Browser mode supports the core conversion features: message rendering, photo embedding, timestamp formatting, and sender attribution. It produces a clean, well-formatted PDF that is suitable for personal archives and straightforward use cases. Pro legal features - Bates-stamp numbering, SHA-256 integrity hashing, PII redaction, and enhanced audio card rendering - are only available in server mode.

Server mode also provides a richer rendering of the chat bubbles because it uses a headless Chromium browser with the full WhatsApp CSS applied, rather than the pdf-lib implementation used in browser mode. The result is a PDF that more closely matches the visual appearance of WhatsApp as you experience it on your phone - a difference that matters for legal exhibits and premium personal archives. See the <a href='/pricing'>WaChat to PDF plans</a> comparison for the full feature breakdown.

When to Use Browser Mode

Browser mode is the right choice for chats under 300 MB where all the content you need can be produced without legal features. It is also ideal when the chat contains highly sensitive information and you need an absolute guarantee that it does not leave your device. Personal memory archives, informal dispute reference documents, and situations where you simply want a quick, private conversion all fit well in browser mode.

The free plan uses browser mode by default, making it a zero-cost option for standard conversions. If you find that browser mode is slow on a particular device or that your export is too large, the path of least friction is to export the chat without media (dramatically smaller file) and re-process in browser mode, or to upgrade to the pro plan for server mode.

When to Use Server Mode

Server mode is the right choice for any export where legal features are needed - Bates numbering for court exhibits, SHA-256 hashing for integrity certification, or PII redaction before sharing. It is also the practical choice for large files above 300 MB, for users on slower devices where browser processing would be impractical, and for situations where you want to queue multiple conversions without tying up your device.

The Server Data Deletion Promise

WaChat to PDF's server mode automatically deletes all uploaded files and processed output within 24 hours of the completed PDF being downloaded. The deletion is automated and does not require any action on your part. After 24 hours, if the download link has not been used, the file is also deleted - no WhatsApp content persists on the servers beyond the minimum time needed to produce and deliver the PDF.