The best timeframe to trade a trendline depends on your style: 4-hour for swing trades, daily or weekly for position trades, and 1-hour or 15-minute for day trading.
Day traders may prefer 15-minute to 1-hour charts, swing traders often use 4-hour or daily charts, and longer-term traders opt for weekly or monthly charts to capture broader trends.
Higher timeframes produce stronger, more reliable lines because they capture true structural turns and filter out intraday noise.
The 4-hour chart catches clean swing moves and filters out the extra noise found on lower timeframes, making it the sweet spot for most discretionary traders.