# Mac running slow? Eight causes and how to fix each one > Why a Mac or MacBook runs slow and how to speed it up: check memory pressure, runaway apps, a full disk, login items and more. - URL: https://maccleaner.tech/mac-running-slow/ - Published by: Mac Cleaner Guide, written by the Bytesweep team (Bytesweep is the publisher's own app) - Last updated: November 12, 2026 - Steps checked against Apple's documentation for macOS 27 in November 2026. A slow Mac usually has one of three problems: an app using too much processor, too little free memory, or a nearly full disk. Open Activity Monitor to check the first two and Storage settings to check the third. Fix the one you find instead of running every tip you can find. ## Diagnose first: two minutes in Activity Monitor Open Activity Monitor from Applications > Utilities, or search for it with Spotlight. - **CPU tab.** Click the **% CPU** column to sort. An app sitting near or above 100 percent for minutes is your culprit. - **Memory tab.** Look at the **Memory Pressure** graph at the bottom. Green is fine. Yellow is a warning that the Mac may need more memory, and red means it needs more than it has. ## 1. A runaway app Select the app in Activity Monitor and click the stop button in the toolbar, then **Quit** or **Force Quit**. If the same app does it repeatedly, update it. Browser tabs appear as separate processes, so a single heavy page can be the cause. ## 2. Not enough memory With memory pressure in the yellow or red, close apps and browser tabs you are not using. Browsers are the heaviest users on most Macs. Memory in a modern Mac cannot be upgraded, so the only lasting fixes are running less at once or, eventually, a Mac with more. Be wary of "memory cleaner" apps that promise to free RAM. macOS already manages memory, and unused memory is not a benefit. Forcing it empty mostly makes the next app launch slower. ## 3. A nearly full disk macOS needs free disk space for swap and temporary files. When the disk is almost full, everything slows down, and the Mac may show the spinning wheel on simple tasks. Check **System Settings > General > Storage**. Apple gives no exact figure; as a rule of thumb, if less than about 10 percent is free, work through [how to free up space on a Mac](https://maccleaner.tech/free-up-space-mac/). This is the most common fixable cause of a slow older Mac. ## 4. Too many login items Apps that open at login lengthen startup and stay running in the background. Go to **System Settings > General > Login Items & Extensions** (called Login Items on macOS 13 and 14). Remove what you do not need from **Open at Login**. Under **App Background Activity**, switch off apps that have no reason to work when they are closed. You can turn them back on. ## 5. It has not been restarted in weeks A restart clears swap, closes stuck processes and applies pending updates. If your Mac has been up for a month, restart it before trying anything else. ## 6. Indexing after an update After a macOS upgrade or a large file transfer, Spotlight and Photos re-index in the background. In Activity Monitor these appear as `mds`, `mdworker` and `photoanalysisd`. This is expected and ends by itself. Apple says indexing can take hours or even days, depending on how much data you have, and finishes sooner when the Mac is idle, plugged in and online. Leave it connected overnight. ## 7. Out-of-date software Install pending updates from **System Settings > General > Software Update** and update your apps. Performance bugs are fixed in point releases more often than people expect. ## 8. Heat A Mac that is hot slows its processor to protect itself. Use it on a hard surface, not a bed or a cushion, and keep it out of direct sun. In Activity Monitor, a process called `kernel_task` using a lot of CPU is macOS deliberately holding the processor back to cool it down. Apple notes this can happen even when the Mac does not feel hot to the touch. ## What does not help - Clearing caches as a speed fix. Caches exist to make things faster; clearing them helps a misbehaving app or a full disk, not general speed. - Apps that report hundreds of "issues" after a free scan. - Reinstalling macOS before you have checked the causes above. ## When it is the hardware If memory pressure is red with only a browser and a mail app open, or the Mac can no longer run the current macOS, it has reached the limit of what software can fix. Cleaning will still give you a tidier disk, but not a faster processor. One 2026 change is worth knowing: macOS 27 Golden Gate, released in September, runs only on Macs with Apple silicon, so no Intel Mac can install it. **Where our own app helps, and where it does not.** Bytesweep fixes the full-disk cause: it shows what fills the disk and cleans it. It will not add memory or cure a runaway app. This site is published by the Bytesweep team. Free to try for 3 days; cleaning needs the one-time USD 29.99 license. [See Bytesweep for Mac](https://bytesweep.app/mac.html). ## Quick answers ### Why is my Mac running slow? Usually one of three things: an app using too much processor, too little free memory, or a nearly full disk. Activity Monitor shows the first two and Storage settings shows the third. ### Does a full disk slow down a Mac? Yes. macOS needs free space for swap and temporary files. Apple gives no exact figure; as a rule of thumb, trouble starts below about 10 percent free. ### Do memory cleaner apps speed up a Mac? No. macOS manages memory itself, and forcing memory empty mostly makes the next app launch slower. ## Sources - [Mac User Guide: If your Mac runs slowly](https://support.apple.com/guide/mac-help/if-your-mac-runs-slowly-mchlp1731/mac) - [Activity Monitor User Guide: Check if your Mac needs more RAM](https://support.apple.com/guide/activity-monitor/check-if-your-mac-needs-more-ram-actmntr34865/mac) - [Apple Support: If kernel_task is using a large percentage of your Mac CPU](https://support.apple.com/en-us/102172) - [Apple Support: About Spotlight indexing and search results](https://support.apple.com/en-us/102321) - [Mac User Guide: Change Login Items & Extensions settings on Mac](https://support.apple.com/guide/mac-help/change-login-items-extensions-settings-mtusr003/mac) - [Apple Support: macOS 27 Golden Gate is compatible with these computers](https://support.apple.com/en-us/127255)