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② 後台搜尋「BackupBridge – Free Backup & Migration」→ 直接安裝（推薦）
原文外掛簡介
BackupBridge is a free all-in-one WordPress backup, restore and website migration plugin. Need a free WordPress backup plugin for large sites? Export your site into a portable backup, upload a backup to another WordPress installation, and restore your database, media, themes, plugins and settings. Local backup import and export are free, with no paid upgrade or built-in fixed total-backup size cap. Large transfers use resumable chunks and integrity verification.
Free backup, import and export features
Free full-site backup and export: Save your WordPress database and wp-content data together in a portable .usm archive.
Free backup import and restore: Upload a supported backup from your computer, or restore a backup already present on your server.
Unlimited-size local backups (host-dependent): No plugin-imposed total archive size limit and no premium unlock for larger local backups. Actual limits depend on your host, free disk space, PHP, database settings and available resources.
Large-file migration: Chunked, resumable uploads with per-chunk SHA-256 checks, plus checkpointed site restore workflows.
Move sites between domains and hosts: Database-aware URL replacement helps migrate a site to its destination.
Selective restore and recovery: Choose content to restore, use preflight checks and rollback workflows to reduce the risk of a failed migration.
Database and files included: Back up WordPress content, images and other uploads, themes, plugins and site settings.
Multiple file formats: Native .usm export/import, supported .zip import and classic uncompressed .wpress compatibility. Compressed or encrypted .wpress variants may not work.
Local admin tools: Backup management, diagnostics and WP-CLI commands.
No subscription is needed for these local backup, import, export and restore capabilities. This does not mean unlimited server storage or guaranteed success on every host. Check available disk space and database permissions, and test restores on a staging site before migrating production content. Built-in cloud import and export are not currently available.
How backups and restores work
The native .usm backup contains the WordPress database and wp-content data. Restore jobs use durable checkpoints, integrity checks, staged database activation and rollback procedures designed to reduce restore risks. Hosting limits and database privileges affect results.
The live database is modified by exactly one atomic RENAME TABLE; WordPress never sees a missing table.
Live files are moved (never deleted) into a journaled rollback area until the final health check passes.
Restore failures are handled by recovery and rollback workflows; verify recovery on a staging site before relying on it for production.
A private maintenance marker is used during site restore.
Keyset search/replace with no LIKE ‘%needle%’ scans, binary-safe columns, no-primary-key table support and oversized-value handling.
Streamed oversized rows, views/triggers, generated columns, exactly-once transactional import, destination privilege/packet/collation/storage preflight.
Per-chunk SHA-256 uploads with resumable server-side verification (no size cut-off).
Selective restore, mirror mode, orphan cleanup, WP-CLI commands and a fault-injection test matrix.
Supported formats:
* .usm — recommended native compact streaming backup with per-entry integrity checks and database integrity metadata
* .zip — legacy/native-compatible archive import
* .wpress — classic uncompressed compatibility mode; newer compressed/encrypted variants may not be supported
Human-readable source and build instructions
The complete, human-readable original JavaScript source is included in src/admin.js. The
matching authored stylesheet is src/admin.css. Both files are included in this ZIP and
neither is produced from private, inaccessible source. No third-party bundled/minified
JavaScript libraries are distributed, and no npm, Composer or webpack dependencies are
required. Readable developer source is maintained in src/admin.js and src/admin.css. The
plugin serves the whitespace-compacted assets/js/admin.min.js and
assets/css/admin.min.css files in production, and the original readable sources
when SCRIPT_DEBUG is enabled. Both sets are shipped in the plugin ZIP.
The build is reproducible without npm dependencies: run
python3 tools/build_assets.py
from the plugin root. This removes only redundant line indentation and empty
lines; it does not rewrite JS tokens or change string contents. The readable
assets/js/admin.js and assets/css/admin.css are retained as compatibility copies.
Serving the compact asset is an admin-only optimization (not a measured improvement
to public-site page load speed).
Security and performance notes
Only users with manage_options and a valid AJAX nonce can start ordinary migration operations.
During a database restore, migration-specific bearer tokens can authorize the remaining checkpoint calls because the restored database can invalidate the original WordPress login.
Backup deletion is restricted to supported archive filenames physically located in this plugin’s backup directory (no symlinks).
Migration and restore deliberately execute multiple SQL statements per batch and read large fields in bounded slices so PHP memory, database packet limits, journal semantics and resume checkpoints remain safe. These are not normal frontend page-load queries and cannot safely be merged into one bulk query.
Similarly, uncached HTTP probes are intentional: a fresh status check is needed on each migration/rollback, and cached responses would risk releasing broken sites.
The admin-only JS/CSS is loaded only on Site Migrator screens, not the public frontend or other admin screens.
