# How to enable Redis or Memcached > Give WordPress a persistent object cache so database query results survive between requests — connect Redis or Memcached with one click, or configure the connection by hand. - Category: Cache - Canonical: https://xspeedcache.com/docs/object-cache/ --- WordPress caches database results in memory while it builds a page — then throws them away. The next visitor's request starts from nothing and re-runs the same queries. A **persistent object cache** keeps those results in Redis or Memcached so they survive between requests, which is the biggest win available to sites that are database-heavy rather than traffic-heavy: WooCommerce stores, membership sites, anything with complex queries. > **Where to find it** > > 1. In your WordPress admin, click **xSpeed Cache** in the left menu. > 2. In the xSpeed Cache sidebar, open the **Cache** group. > 3. Click the **Object Cache** card. > > *Shortcut: open `wp-admin/admin.php?page=xspeed#/cache/object-cache` directly.* > > ✅ This panel is part of **xSpeed Cache (Free)**. ![Object cache status and one-click setup](https://xspeedcache.com/_astro/object-cache-status.B9G2tOX3.png) 1. **Status** — whether a persistent cache is active, and what your server supports. 2. **One-click setup** — test the connection, then let xSpeed do the wiring. --- ## Settings at a glance | Setting | Default | What it does | | --- | --- | --- | | **Backend** | Redis | Which cache server you intend to use. | | **Redis Host** | 127.0.0.1 | Hostname or IP of the Redis server. | | **Redis Port** | 6379 | Range 1–65535. | | **Redis User** | Blank | Only for Redis 6+ ACL users. | | **Redis Password** | Blank | Leave blank if Redis runs without auth. | | **Redis Database** | 0 | Logical DB number, 0–15. | | **Memcached Host** | 127.0.0.1 | Shown only when Backend = Memcached. | | **Memcached Port** | 11211 | Range 1–65535. | | **Cache Key Prefix** | Blank | Salt that isolates this site's keys. | | **Connection Timeout** | 1 s | How long to wait for a connection. | | **Persistent Connections** | On | Reuse connections across PHP requests. | The Redis and Memcached fields are **mutually exclusive** — the panel shows only the set matching your chosen **Backend**. On a managed host, some of these may already be set for you in `wp-config.php` and appear read-only — see **Settings defined in wp-config.php** below. --- ## How it works WordPress keeps database results in memory only for the life of a single request. A persistent object cache moves that store into Redis or Memcached, which keeps running between requests — so the next request reuses results instead of re-querying. Enabling it installs an `object-cache.php` drop-in into `wp-content/` and adds connection constants to your `wp-config.php`. WordPress then routes its cache API through your cache server automatically; no theme or plugin changes are needed. --- ## Start here: check the status The top card tells you two separate things, and it's worth reading carefully before you touch anything: - **Whether a persistent object cache is active.** "No persistent object cache" means WordPress is using its built-in in-memory cache, which resets on every request — so nothing is actually persisting. - **What your server can support.** A **Redis ready** badge means the native `phpredis` extension was detected, which is the fastest path. Without a badge here, your host doesn't have a cache server available and nothing else on this panel will help — that's a hosting question, not a settings one. **Re-detect** re-runs the check, which is what you want after your host enables Redis for you. Two states on that card are worth recognising, because both look like a working cache at first glance: - **Connected, but storing nothing.** The connection succeeds but the server refuses every write, so nothing is ever cached. On managed hosting this is almost always a **Cache Key Prefix** that doesn't match the namespace your host granted — see that section below. - **Another plugin owns the object-cache drop-in.** xSpeed will not overwrite or remove another plugin's `object-cache.php`. Turn that plugin's object cache off first, then enable xSpeed's. > 💡 **This is the opposite of Page Cache, on purpose.** Turning [Page Cache](https://xspeedcache.com/docs/page-cache/) on can take over another plugin's `advanced-cache.php` once you confirm. The object cache never does — its drop-in stays with whoever installed it. --- ## The easy path: one-click setup If the status card says your server is ready, use **One-click setup** and skip the manual configuration entirely. **Test connection** tries to reach the cache server with your current settings and reports back. Always do this first — it's the difference between finding out now and finding out via a broken site. **Enable object cache** then does the wiring for you: it writes the `object-cache.php` drop-in into `wp-content/` and adds the necessary constants to your `wp-config.php`. No manual file editing, no pasting snippets. > 💡 **Test before you enable.** If the connection fails after the drop-in is in place, WordPress tries to reach a cache server that isn't answering on every request. Testing first turns a potential outage into a message on screen. --- ## Connection settings ![The object cache connection settings](https://xspeedcache.com/_astro/object-cache-connection.DvIVEqGa.png) 1. **Backend** — Redis or Memcached. 2. **Redis Host** — `127.0.0.1` for a server on the same machine. 3. **Redis Port** — 6379 by default. 4. **Redis User** — only for Redis 6+ ACL setups. 5. **Redis Password** — blank if your server has no auth. 6. **Redis Database** — 0–15, to separate sites sharing one server. 7. **Cache Key Prefix** — the salt that isolates this site's keys. Most of these you'll never change. `127.0.0.1` and `6379` are correct whenever Redis runs on the same machine as PHP, which is the common case. **Redis User** is the one people get wrong. Leave it blank unless your host explicitly issued you a Redis ACL user (a Redis 6+ feature). Legacy password-only Redis authenticates as the default user, and putting something here will break that. **Redis Database** (0–15) matters when several sites share one Redis server: give each its own number and they can't tread on each other. ### Using Memcached instead ![The Memcached connection settings](https://xspeedcache.com/_astro/object-cache-memcached.DJC-I4K5.png) 1. **Backend** — switched to Memcached. 2. **Memcached Host** — `127.0.0.1` for a server on the same machine. 3. **Memcached Port** — 11211 by default. 4. **Cache Key Prefix** — same role as with Redis. Switch **Backend** to **Memcached** and the form changes: the Redis fields disappear and two Memcached fields take their place. There are only **two**, because Memcached has no equivalent of Redis's user, password, or database-number options — it's a simpler protocol with no built-in authentication and no logical database separation. That last point used to matter a great deal: with no database numbers to separate them, sites sharing one Memcached server depended entirely on each one setting a **Cache Key Prefix**. They no longer do. Every site's cache keys are now namespaced automatically, whichever backend you use, so sites sharing a server can't read or purge each other's entries even with the prefix left blank. If your host already configures Memcached through the standard `$memcached_servers` array in `wp-config.php`, xSpeed reads the host and port straight from it. | | Redis | Memcached | | --- | --- | --- | | **Default port** | 6379 | 11211 | | **Authentication** | Optional password, plus ACL users on Redis 6+ | None | | **Separating sites** | Automatic — plus a database number or key prefix if you want | Automatic — plus a key prefix if you want | | **Recommended?** | Yes, if available | Only if Redis isn't offered | Because the two field sets are mutually exclusive, **your Redis settings aren't lost when you switch** — they're stored separately and reappear if you switch back. ### Cache Key Prefix — read this if your host is managed **On an ordinary server, leave it blank.** The prefix is the salt that keeps this site's cache keys apart from every other site's. Left empty, xSpeed uses one unique to this install — WordPress's own `WP_CACHE_KEY_SALT` if your `wp-config.php` defines one, as nearly every install does, or otherwise one derived from the site address, database name and table prefix. Either way, sites sharing a server never collide. **On ACL-namespaced Redis, it must match your host's value.** On hosts such as xCloud, Redis only allows writes inside a namespace the host assigns, often shown as "Redis Object Cache Key". A prefix that doesn't match gets every write refused with a `NOPERM` error and nothing persists. That is exactly what the status card reports as **Connected, but storing nothing** — the connection tests fine, yet the cache never fills. Most managed hosts write that value into `wp-config.php` as `WP_REDIS_PREFIX`, and xSpeed picks it up on its own — the field shows it as defined there rather than asking you to paste it. If your host only displays the key in its dashboard, copy it into this field. > 💡 **`WP_CACHE_KEY_SALT` never locks this field.** Nearly every WordPress install defines it with a random value, so it isn't treated as a namespace your host chose — the field stays blank and editable. It's still honoured as the salt at runtime when nothing more specific is set. --- ## Advanced settings ![Connection timeout and persistent connections](https://xspeedcache.com/_astro/object-cache-advanced.DLXWzQbJ.png) 1. **Connection Timeout** — how long to wait before giving up. 2. **Persistent Connections** — reuse connections across requests. **Connection Timeout** defaults to **1 second**, and low is correct. This is the time WordPress waits for the cache server before giving up. If the cache is unreachable, a short timeout means a brief stumble; a long one means every page hangs for that duration. Keep it at 1–2 seconds so a misconfigured cache can never stall your site. **Persistent Connections** is on by default and generally a win — reusing a connection across PHP requests avoids the handshake each time. Turn it off only if your cache server complains about idle connections piling up. --- ## Settings defined in wp-config.php Managed hosts often configure Redis for you by writing constants into `wp-config.php` before you ever open this panel. xSpeed reads them, and a field set that way is shown **read-only**, with a note naming its source — *"Defined in wp-config.php as `WP_REDIS_HOST`"*. That's deliberate: the host's value is what the drop-in is actually using, so letting you type a different one here would make the panel disagree with the site. For each field, the first of these that is defined wins; if none is, your saved value is used, then the default: | Field | Read from | | --- | --- | | **Redis Host** | `XSPEED_OC_HOST`, `WP_REDIS_HOST` | | **Redis Port** | `XSPEED_OC_PORT`, `WP_REDIS_PORT` | | **Redis User** | `XSPEED_OC_USER`, `WP_REDIS_USER`, or `WP_REDIS_PASSWORD` in its two-part user-and-password form | | **Redis Password** | `XSPEED_OC_PASSWORD`, `WP_REDIS_PASSWORD` | | **Redis Database** | `XSPEED_OC_DATABASE`, `WP_REDIS_DATABASE` | | **Memcached Host** / **Port** | The `$memcached_servers` array, then `XSPEED_OC_MC_HOST` / `XSPEED_OC_MC_PORT` | | **Cache Key Prefix** | `XSPEED_OC_SALT`, `WP_REDIS_PREFIX` | | **Connection Timeout** | `XSPEED_OC_TIMEOUT`, `WP_REDIS_TIMEOUT` | | **Persistent Connections** | `XSPEED_OC_PERSISTENT`, `WP_REDIS_PERSISTENT` | `XSPEED_OC_*` are xSpeed's own names, and they win over the `WP_REDIS_*` names other Redis plugins use. A constant defined as an empty string still counts: on a server with no Redis password, `WP_REDIS_PASSWORD` set to `''` is an answer, not a gap for a saved value to fill. A save that tries to change a defined field is refused with a message naming the constant, so you always know where the real value lives. > 💡 **Only this panel works this way.** In this release the Object Cache connection fields are the only settings in xSpeed that read `wp-config.php` constants. Every other panel stores its settings as normal. ### Managing a defined setting here instead Click the pencil beside a read-only field to take it over. xSpeed asks first — *"Manage this setting here?"* — and spells out the trade: once you manage it here, later changes your host makes to that constant are ignored. On a managed host such as xCloud or Cloudways, changing the value in their control panel is usually the better route. Confirm with **Manage here**, and your next save stores the value like any other setting. The field then reads *"Your value is used instead of `WP_REDIS_HOST` from wp-config.php"*, with **Use the host value** beside it to hand the setting back. The host's constant takes over again immediately. --- ## Related - [How to enable Page Cache](https://xspeedcache.com/docs/page-cache/) - [How to clean up your database](https://xspeedcache.com/docs/database/) - [How to read your cache diagnostics](https://xspeedcache.com/docs/cache-diagnostics/) - [How to get support](https://xspeedcache.com/docs/help-support/)