A laggy chart costs you entries. The causes are almost always local, and they're fixable in about ten minutes.
Start with the biggest wins
1. Reduce indicator count. Each indicator recalculates on every tick, and complex scripts that reference higher timeframes or loop over history cost far more than simple ones. Five well-chosen indicators outperform twelve, both for performance and for decision quality — see combining indicators without clutter.
2. Reduce visible bars. Zoom in. Rendering thousands of bars with several plots each is expensive, and you don't make decisions from bars off the left edge of the screen.
3. Close spare layouts and tabs. Multi-chart layouts multiply everything by the number of panes. A four-chart layout with six indicators each is twenty-four running scripts. Browser tabs with other charts open keep computing in the background.
4. Remove drawings you no longer use. Hundreds of accumulated lines, boxes and text objects have a real cost, especially when set to appear on all timeframes. Open the object tree and prune.
Then the environment
Browser: restart it. Long-lived sessions accumulate memory. Disable extensions one at a time if the problem persists — ad blockers and script blockers are common culprits with charting sites. Hardware acceleration should be on in your browser settings.
Desktop app vs browser: the desktop application usually performs better with heavy layouts because it isn't competing with everything else in your browser.
Machine: charting is GPU-assisted. An old integrated graphics chip with several external monitors will struggle regardless of settings. Check whether other GPU-heavy apps are running.
Connection: open a speed test while the chart is lagging. Streaming tick data on an unstable connection produces stuttering that looks like a performance problem but isn't.
