OnceOnly Zapier integrationAutomate OnceOnly with Zapier.
OnceOnly Zapier integration: 0 triggers, 1 action, 0 searches. OnceOnly does one job inside a Zap: its Check & Lock action checks a key you choose and locks it, so the same event cannot run the rest of the Zap twice. It never starts a Zap on its own.
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What the OnceOnly Zapier integration actually does
OnceOnly is a duplicate guard for automations. In Zapier it adds a single step, Check & Lock, that you place after the trigger: it looks at a value that identifies the event, such as an order number, and locks it for a period you set. If the same value shows up again while the lock holds, the event is treated as a repeat.
Three results people build with it. A confirmation email that goes out once per order: the order number becomes the key, so an order that reaches the Zap twice does not send two emails. A clean spreadsheet: a message or event number keyed through Check & Lock keeps a log sheet from filling with copies of the same line. An invoice or a payment that is only recorded once in your accounting tool, which is where a duplicate hurts the most.
What Zapier does not do for OnceOnly is just as clear. There is no trigger, so OnceOnly cannot start a Zap: another app always comes first. There is no search either. And the Zapier listing does not describe what the step hands back after a check, or whether it halts the Zap by itself on a repeat; you find out by testing the step and reading the result before you build what comes after.
If you are weighing other tools for this kind of guard, Make vs Zapier and n8n vs Zapier are the pages to open next.
Zapier vocabulary in one minute
Eight words come back on every Zapier screen. Here they are in plain English, once, before the rest of the page uses them.
- Zap
- The automation you build: one trigger, then one or more actions that run each time the trigger event happens.
- Trigger
- The event in an app that starts the Zap. OnceOnly has none, so the trigger always comes from another tool.
- Action
- What the Zap does after it starts. Check & Lock is an action: it runs after the trigger, like any other step.
- Task
- The unit Zapier bills. One task equals one action your Zap completes successfully; your plan counts those.
- Polling vs instant trigger
- A polling trigger is checked on a timer. An instant trigger is reported by its app the moment the event happens.
- Filter
- A step that lets the Zap continue only when the incoming item meets a condition you set, and stops it otherwise.
- Connection
- Your OnceOnly account linked to Zapier once, then reused by every Check & Lock step in every Zap you build.
- Multi-step Zap
- Any Zap beyond one trigger and one action. A second action or a filter makes it one, and it then needs a paid plan.
What it really costs you
Short version: Check & Lock is an action, so each successful check costs a task, and it nearly always lives in a multi-step Zap.
- Trigger (another app)0 tasks
- Check & Lock that succeeds1 task
- Free plan100 tasks a month, 2 steps per Zap
- Premium appNo
The trigger of your Zap never costs a task. Each action that succeeds counts once, and Check & Lock is one of them, so a Zap with a trigger, Check & Lock and an email uses two tasks per event; an action that fails is not counted. The free plan gives 100 tasks a month and unlimited Zaps, but stops at two steps, one trigger and one action. A guard only makes sense with something after it, so in practice a OnceOnly Zap is multi-step and needs a paid plan. OnceOnly is not a premium app. How often the first step is checked depends on the trigger of the other app and on your plan, as the grid shows.
Connect your OnceOnly account in 3 steps
- 01
Open the Apps page
In your Zapier account, go to Apps and click + Add connection. You need a OnceOnly account before you start; Zapier only links an account that already exists.
- 02
Find OnceOnly
Type OnceOnly in the search box of the dialog, pick it from the list, then click Add connection. Zapier keeps this connection and reuses it in every Zap where you add Check & Lock.
- 03
Sign in and grant access
A tab opens on OnceOnly. Sign in with your account and grant Zapier access to it. Back in Zapier, the connection shows on the Apps page and is ready to use in a Zap.
Your first OnceOnly Zap, step by step
GoalEach new order sends one confirmation email, even if the same order reaches the Zap twice.
- 01
Build: pick the starting app
Create a Zap and pick the app and event that start it, here a new order in your shop. OnceOnly has no trigger, so the first step always belongs to another tool.
- 02
Test the trigger
Run the trigger test. Zapier brings back the three most recent items of the connected account, so you can pick a real order and see which value identifies it.
- 03
Add Check & Lock
Add OnceOnly as the next step and choose Check & Lock. Map the order number into Key, and set the TTL, in seconds, to how long a repeat should stay blocked.
- 04
Test and read the result
Test the step and read what came back. That result is what the next step can rely on, so check it before you add the email. This makes the Zap multi-step: it needs a paid plan.
- 05
Add the email, then publish
Add the Gmail action, test it once, then publish the Zap to switch it on. Each order then uses two tasks: one for the check, one for the email.
The OnceOnly action
OnceOnly gives you 1 action. For each one: what it does for you, when to reach for it, and what to watch out for.
Check & Lock
ActionIn Zapier“Checks a key and locks it once to prevent duplicate runs.”
Looks at the key you give it and locks that key once, so a repeated event with the same key is recognised as a duplicate while the lock lasts.
When a OnceOnly Zap breaks
Zapier attaches no help article and no specific limit to OnceOnly. What goes wrong comes from the key you choose and from the way every Zap works.
Four cases cover most OnceOnly Zaps that misbehave. If yours matches none of them, the Zapier troubleshooting page is the next stop.
Real events get blocked
If the key is not unique to each event, for example a customer name instead of an order number, Check & Lock treats new events as repeats while the lock holds.Old events are not covered
A Zap only reacts to what happens after it is switched on. Events from before are never checked or locked; dealing with that backlog is a separate job.The Zap keeps restarting itself
A Zap that writes into the place its own trigger watches sets itself off again and again. A new run often brings a new key, so the guard may not stop it.A big batch is held back
When the trigger app suddenly returns a huge batch, after a bulk import or a migration, Zapier's flood protection can hold those runs back before they reach the check.
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