To move replay data around, you must first understand its format. PostHog uses (record and replay the web), an open-source library that records web sessions into a serialized stream of events. Instead of taking heavy video recordings, PostHog captures:

2. The Reverse Proxy and SQLite Buffer (The Hybrid Edge Pattern)

It monitors every change to the DOM, mouse movement, click, and window resize as a stream of JSON text events.

const express = require('express'); const fs = require('fs'); const path = require('path'); const cors = require('cors'); const app = express(); app.use(cors()); // PostHog payloads can be large; ensure payload limits are high app.use(express.json( limit: '50mb' )); app.use(express.urlencoded( extended: true, limit: '50mb' )); const STORAGE_DIR = path.join(__dirname, 'posthog_buffer'); if (!fs.existsSync(STORAGE_DIR)) fs.mkdirSync(STORAGE_DIR); // Intercept PostHog batch and session recording endpoints app.post('/e/', (req, res) => const timestamp = Date.now(); const filename = path.join(STORAGE_DIR, `event_$timestamp.json`); fs.writeFile(filename, JSON.stringify(req.body), (err) => if (err) console.error("Failed to save local replay chunk:", err); return res.status(500).send("Storage Error"); // Respond with success so the frontend SDK purges its internal memory res.status(200).json( status: 1 ); ); ); // Alias for session recording specific endpoints if used by the SDK version app.post('/s/', (req, res) => const timestamp = Date.now(); const filename = path.join(STORAGE_DIR, `replay_$timestamp.json`); fs.writeFile(filename, JSON.stringify(req.body), (err) => if (err) return res.status(500).send("Storage Error"); res.status(200).json( status: 1 ); ); ); app.listen(8080, () => console.log('Portable PostHog Buffer running on port 8080')); Use code with caution. Step 3: The Background Sync Processor

: Every recording includes related user data, events, and feature flag variants, plus triggered errors. Debugging Power : The platform provides advanced tools to inspect console logs network calls

private replayEventsUpToIndex(index: number): void for (let i = 0; i <= index; i++) this.replayEvent(this.recording.events[i]);

Running session replay on a local machine during User Acceptance Testing (UAT) allows engineers to catch edge-case visual bugs, state management failures, and race conditions before code ever hits a staging server. 3. Mobile and Field Testing

Portable data must still be secure. PostHog protects your private user information even when replays move outside the platform.

Storing raw session recordings locally on a user's machine creates security vulnerabilities. If the machine is compromised, an attacker could read the raw text files containing everything the user did in the app.

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If you need complete data portability for long-term storage, you can export your raw session recording events. Using PostHog's real-time data pipelines or Batch Exports, you can automatically route replay data into cloud storage warehouses such as: Google Cloud Storage