If you make social posts for other people, you already have an approval process. It is probably email, or WhatsApp, with the files attached and the word "thoughts?" underneath.
It works, in the sense that posts do eventually get approved. What it does not do is leave a record. Three weeks later nobody can find who said yes, and the change your client wanted arrived as a phone call you took while driving.
Why the proper tools go unused
The approval tools built for this all do the same thing: your client gets an invitation, creates an account, sets a password, and answers inside the tool.
That is a perfectly good design and it is why most of them sit unused. Every one of those steps is a place where a busy person who does not care about your software stops. You are not asking them to approve a post; you are asking them to onboard.
Freelancers and small agencies feel this hardest, because the relationship is informal. You cannot send a plumber with forty staff an invitation to a collaboration platform and expect a password to get set.
The other trade
So the alternative is a link that needs nothing. Open it, look, answer, close.
It has a real cost and it is worth stating rather than discovering: whoever holds the link can answer it. If your client forwards it to a colleague, that colleague can approve the post. There is no identity check, because adding one is exactly the signup wall this exists to remove.
For most of the work most people do, that trade is obviously right. Approving a carousel about a boiler service is not a legal signature, and the person who forwarded it chose to forward it.
For some work it is obviously wrong. If approval must come from one named individual and you may have to prove later that it did, use email — a reply from a known address is weak evidence, but it is evidence, and a link cannot give you that.
Deciding which category you are in takes about five seconds and almost nobody does it, which is why it is worth saying out loud.
What to look for
If you are evaluating something for this, three questions get you most of the way:
Does the client need an account? If yes, assume a meaningful share of your clients will not complete it and plan accordingly.
Can you revoke a link? An approval link that lives forever is a document you have lost track of. Someone finding an old thread and approving something you changed your mind about in August is the realistic failure, not a stranger guessing a URL.
What does it record about the person who opened it? This is the one nobody asks. Your client never signed up to anything, agreed to nothing, and is not your software's user. Logging their IP and location so you can see "opened from Athens on an iPhone" is surveillance of somebody who is not party to the arrangement. It should tell you that it was opened, and when. Not who.
What changes when there is a record
The useful part is not the yes. It is the shape of what comes back.
When a client has two buttons — approve, or ask for one change — the change arrives as a sentence. "Can we not lead with price." That is actionable in a way that "call me about the posts" is not, and it stays attached to the post rather than scrolling out of a thread.
And the states that are not an answer turn out to matter just as much. Opened and not replied and never opened look identical in email and need opposite follow-ups: one is a person thinking about it, the other is a message that never arrived. Any approval link worth using should separate those two, because chasing the wrong one is how you become annoying.
In PostPop this is on the Agency plan and AppSumo Tier 3: copy a link, send it in whatever thread you already use, 30 days, revocable, opens counted and never attributed. The full guide is here.