Complete Guide to Support and Resistance
— Role Reversal, Judging Strength, and Practical Use
Support is the price level where a decline tends to bounce; resistance is the price level where selling pressure concentrates during a rally. These two concepts are the foundation of all technical analysis, and understanding role reversal makes your entry and stop-loss criteria after a breakout much clearer.
Why Support Forms
Support forms once a price level builds up a history of bounces. The logic is simple. Since many investors bought at that level in the past, when the price comes back down to it, additional buying rushes in on the expectation that "it'll go up again." This concentrated demand halts the decline and produces a bounce.
Near a 52-week low, the bottom of a prior trading range, or the floor of a long consolidation — these are classic support levels. The more times a level gets touched, the more strongly it sticks in investors' memory, and the stronger the support effect becomes.
Why Resistance Forms
Resistance forms from the opposite psychology. Investors who bought at that level and are now sitting on a loss prepare a sell order with the thought, "I'll sell once I get back to break-even." When the price reaches that level again, that prepared supply hits the market all at once, acting as a ceiling that caps the rally.
A prior high, a 52-week high, or a round psychological price ($100, $200, etc.) often act as resistance for the same reason.
Role Reversal — the Single Most Important Principle
Role reversal is the core principle of support and resistance.
- Resistance → Support: once a resistance level breaks to the upside, that price level flips into new support. The logic is that "everyone who wanted to sell there has already sold, so selling pressure disappears, and buying demand appears on the expectation of further upside."
- Support → Resistance: conversely, once support breaks to the downside, it becomes resistance. The logic is that "everyone who bought there is now sitting on a loss, so selling desire builds up as the price recovers to their break-even."
Judging the Strength of Support and Resistance
Not every support or resistance level carries the same weight. Here are 4 criteria for judging strength.
- Number of touches — the more times a level bounces or rejects at the same price, the deeper it's etched into investor memory, raising its strength. 3 is stronger than 2, and 4 is stronger than 3.
- Volume — the more volume traded in the zone where support or resistance formed, the stronger it is. Heavy volume means a lot of trading happened at that price, so it sticks with more investors' memory.
- Age — older support or resistance tends to act more strongly, since it spans more investors' memory than a recent one. A high from years ago often still acts as resistance today.
- Speed and gap of the break — if the zone broke on a large gap or a sharp move, that zone is more likely to act as strong resistance again on a return visit.
Horizontal vs. Dynamic Support and Resistance
Everything explained so far has been horizontal support and resistance — a horizontal line drawn at a specific price level.
Dynamic support and resistance, by contrast, is a line that moves along with the price. The classic example is a moving average (MA). MA20, MA50, and MA200 become self-fulfilling support and resistance because so many investors use them as a benchmark. See how to use moving averages.
A trendline is another form of dynamic support and resistance. A zone where horizontal support/resistance overlaps with a trendline or moving average tends to produce an especially strong reaction.
Using It in Breakout Trading
The support/resistance concept underlies breakout trading. Entering on a resistance breakout, then re-entering on a retest of the prior resistance (now support), is the role-reversal principle applied in practice. Check today's scan for stocks breaking through resistance.