What are Safe/Unsafe strings?

So, from my understanding, a string is a like a combo, except it doesn’t count up on the combo meter and is normally blocked. Is that right?
So what makes a string safe or unsafe? Obviously, if I string with an unsafe move I can get punished by the blocker, but what makes it technically an unsafe move? And is there any reason to end a string with something that isn’t safe?

Generally speaking, a move is unsafe if it gives your opponent a chance to attack while you’re in recovery frames – it allows your opponent to hurt you for free. So like, if your DP is blocked, there are hella recovery frames where you’re a sitting duck and your opponent can do whatever he wants. The general rule of thumb: alot of recovery frames = unsafe on block.

Besides recovery frames, the safety of a move depends on the range you’re left at after that move is blocked, coupled with your opponent’s attack options at that range. For example, a blocked dragon punch is always (?) unsafe because it leaves you in alot of recovery, at a range where the entire cast has options to punish you. A Blanka-ball is a different story, as there is alot of recovery on the move but it leaves you pretty far from your opponent. Against Ryu, a ball is usually safe on block because Ryu has no attack options that can punish Blanka’s recovery at such a far range – that is, until Ryu has Super. But against Dhalsim, a blocked ball is NEVER safe because Sim’s stretchy arms can get at Blanka while he’s in recovery, even though he’s half-way across the screen.

A blockstring can be safe/unsafe in other ways aside from the last move involved. Unsafe blockstrings have ‘gaps’ in them which allow your opponent to act during that time. Safe blockstrings do not have any of those gaps.

A blockstring of chained attacks is safe. So if you just rapidfire two or three c.jabs with Ryu, that shit is safe – no gaps whatsoever.

Once you introduce a link into your blockstring, the string can either be safe or unsafe depending on frame rates. A link blockstring can be safe if the move AFTER the link has a startup time which is less than the block advantage of the move BEFORE the link (example, after Bison’s “c.jab, s.jab” is blocked, you can safely do a c.short but cannot safely do a c.forward – check the framerates and it’ll make sense!). There are very few of these in SF4, which is why dude just mashed out an uppercut on you in the middle of your string.

What game are you referring to, tomorr0w? It has different answers depending on if we are talking about Tekken, Street Fighter, etc.

A blockstring is safe by definition. If there are any gaps in the string that allow for escapes or reversals, then it’s not a true blockstring. It’s only since the release of SFIV that people started talking about safe and unsafe blockstrings. This is because in SFIV, blockstun is shorter than hitstun so even if a string of attacks combo on hit, there’s no guarantee that it will keep the opponent in blockstun without them being able to interrupt it. By using the frame data it’s easy to see which strings are unsafe on block.

eg. SFIV Ryu’s c.lp puts the opponent into 13 frames of hitstun. It has 2 active frames and 7 frames of recovery, so assuming it hits on the first active frame you will recover 5 frames faster than your opponent (13 - 7 - 1), which means you can link a c.mp (which activates in 4 frames) for a combo. However, if the opponent blocks the c.lp he’ll only endure 10 frames of blockstun, and you will only recover 2 frames faster than him. If you then attempt a c.mp, he will be able to backdash, focus attack or reversal.

This is for Tatsunoko vs Capcom. Some people were talking about an Ippatsuman constantly doing unsafe strings on the livestream of the Cbus fight night.