What is proof of play in DOOH?

Proof of play is a playback log generated by the media player itself: a timestamped record that says content was dispatched and, according to the player's own software, played. It's useful operational telemetry, but it is self-attested. It describes what the player believes happened, not what independently happened on the screen.

What is Proof of Display?

Proof of Display is independent, sensor-based verification of what actually appeared on a screen. A separate device (Vojo's Harvester) observes the display itself, fingerprints the content it sees, and matches that fingerprint to the scheduled campaign. It answers a different question: not "did the player try to show this" but "did this actually appear on the glass."

Is proof of play the same as Proof of Display?

No. Proof of play measures the player's intent and internal state; Proof of Display measures the outcome on the screen, independently of the player. A player can log a successful play while the screen is black, showing no signal, or physically obstructed, and proof of play won't catch any of those. Proof of Display will, because it never asks the player to grade its own work.

Why can't proof of play detect a black screen or no signal?

Because most proof-of-play systems log at the software layer: the player confirms it issued a play command, decoded a file, or rendered a frame in its own pipeline. None of that requires the output to have reached a lit, correctly-connected display.

What about creative wrappers and in-creative verification?

A creative wrapper is measurement code that ships inside the creative and reports from within the player's render. It gives the buy side an independent record of the render, but it measures from the same side of the glass as the player, so it complements Proof of Display rather than replacing it. Vojo offers this as Vojo Passport (content-level verification, never called Proof of Display).

Is Proof of Display patented?

Vojo's Proof of Display method is patented, with granted patents in the United Kingdom and the United States, and a European patent application pending.

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DOOH ad verification, explained

Proof of Play vs Proof of Display

Your player says the ad played. Who else saw it? One kind of proof is the system’s account of its own work; the other is an independent look at the screen. Here’s how to tell which one you’re being handed.

Updated 31 October 20265 min read

Take the one-question test Check what your setup misses →

The short answer

Proof of play says the player tried. Proof of Display says the screen showed. A playback log is the system being checked, reporting on itself, so it records a frozen frame, a dark panel and a wrong input all as successful plays.

One is a claim. The other is an observation.

Proof of play

The log the media player writes about itself: it issued the play, decoded the file and rendered frames in its own pipeline. Useful for running a fleet. But it’s self-attested, and nothing in it needs the picture to have reached a lit, connected screen. On its own it can’t tell a real play from:

A screen switched off, or without power downstream of the player
No signal reaching the panel from a loose or failed cable
The panel on the wrong input
Something physically blocking the screen
A frame rendered inside the player that never left the device

Proof of Display

Starts outside the player. A separate sensor (Vojo’s Harvester) watches the screen, fingerprints what’s genuinely on the glass and matches it to the booked campaign. A fault in the player can’t also take out the thing checking it, and when nothing usable is seen, that’s recorded too. It confirms:

The screen was on and showing an image
The right creative was showing, not a fallback or the wrong input
Black screens, freezes and stuck frames the player never reported
Obstruction: nothing usable to fingerprint means nothing was seen

The one-question test

Would this evidence still exist if the delivery system were lying, broken, or switched off?

Independence has two halves that get blurred together: who reports (the seller, or a third party?) and where they stand (inside the system being checked, or outside it?). Only evidence that passes both answers yes.

Playback logNoIt is the delivery system's own account. If the player is wrong, broken or off, so is the log.
In-creative measurementNoIt's a third party, not the seller, but it lives inside the render. If the panel is dark, it can't tell.
A sensor watching the panelYesIt needs nothing from the player, the CMS, the network, or Vojo to be telling the truth.

That includes us. Proof of Display doesn’t need Vojo to have delivered the ad, and it works on screens running someone else’s CMS and player. If our proof needed our delivery, it would be one more party vouching for itself.

What each method can claim

Capability	Proof of play	In-creative	Proof of Display
Source of evidence	The player's own local log, the device reporting on itself	Measurement code inside the creative, reporting from the player's render	An independent sensor watching the screen from outside the player
What it detects	That content was dispatched and a play event was recorded	That the creative was loaded and rendered in the player's environment	What actually appeared on the glass, matched to the campaign by fingerprint
Independence	Self-attested: the same system that failed is the one reporting the failure	Independent of the operator's log, but still runs inside the player stack	Independent of the player, so it still catches faults the player can't see
Catches a black or frozen screen
Catches wrong input or no signal
Catches physical obstruction
Dispute value with an advertiser	Circumstantial: it's the seller's own record, offered on trust	Stronger than the seller's own log, yet still blind to the physical screen	Evidentiary: a third-party measurement neither side had to take on faith

Which one do you actually need?

Not every screen needs independent verification, and pretending otherwise is how verification gets sold to people who won’t get their money back. The question is what a delivery argument costs you.

Playback logs are enough
Your own content, internal comms, or advertising sold on relationships where nobody has ever asked you to prove a spot. The log answers the questions you actually get asked, and it's already free.
In-creative measurement earns its place
You're the buyer, running one campaign across networks you don't own. You can't fit hardware to somebody else's estate, and you need the same measurement everywhere the creative goes. That's what Vojo Passport is for.
Proof of Display pays for itself
Premium sites, audited buyers, or a rate you're trying to defend. Anywhere you already over-deliver to cover a number you can't prove: that cushion costs more, every flight, than the sensor does once.

Most estates end up mixed: logs everywhere, Passport riding in the creative, and Harvesters (which always ship with Passport) on the sites where proof changes the price. Fitting every screen is rarely the right first move. See what your own setup misses.

Questions people ask

What is proof of play in DOOH?: Proof of play is a playback log generated by the media player itself: a timestamped record that says content was dispatched and, according to the player's own software, played. It's useful operational telemetry, but it is self-attested. It describes what the player believes happened, not what independently happened on the screen.
What is Proof of Display?: Proof of Display is independent, sensor-based verification of what actually appeared on a screen. A separate device (Vojo's Harvester) observes the display itself, fingerprints the content it sees, and matches that fingerprint to the scheduled campaign. It answers a different question: not "did the player try to show this" but "did this actually appear on the glass."
Is proof of play the same as Proof of Display?: No. Proof of play measures the player's intent and internal state; Proof of Display measures the outcome on the screen, independently of the player. A player can log a successful play while the screen is black, showing no signal, or physically obstructed, and proof of play won't catch any of those. Proof of Display will, because it never asks the player to grade its own work.
Why can't proof of play detect a black screen or no signal?: Because most proof-of-play systems log at the software layer: the player confirms it issued a play command, decoded a file, or rendered a frame in its own pipeline. None of that requires the output to have reached a lit, correctly-connected display.
What about creative wrappers and in-creative verification?: A creative wrapper is measurement code that ships inside the creative and reports from within the player's render. It gives the buy side an independent record of the render, but it measures from the same side of the glass as the player, so it complements Proof of Display rather than replacing it. Vojo offers this as Vojo Passport (content-level verification, never called Proof of Display).
Is Proof of Display patented?: Vojo's Proof of Display method is patented, with granted patents in the United Kingdom and the United States, and a European patent application pending.

See Proof of Display on a real play

Book a demo How the Harvester works →

Vojo's Proof-of-Display technology is protected by granted patents in the United Kingdom (GB2583366, GB2597434) and the United States (US 12,176,999), with a European patent application pending.

Next: see the outputA sample Proof of Display reportWhat a buyer receives: a vTrust Score on every play and the evidence behind it.

Proof of Play vs Proof of Display

Updated 31 October 20265 min read

One is a claim. The other is an observation.

Proof of play

A screen switched off, or without power downstream of the player
No signal reaching the panel from a loose or failed cable
The panel on the wrong input
Something physically blocking the screen
A frame rendered inside the player that never left the device

Proof of Display

The screen was on and showing an image
The right creative was showing, not a fallback or the wrong input
Black screens, freezes and stuck frames the player never reported
Obstruction: nothing usable to fingerprint means nothing was seen

Would this evidence still exist if the delivery system were lying, broken, or switched off?

Playback logNoIt is the delivery system's own account. If the player is wrong, broken or off, so is the log.

In-creative measurementNoIt's a third party, not the seller, but it lives inside the render. If the panel is dark, it can't tell.

A sensor watching the panelYesIt needs nothing from the player, the CMS, the network, or Vojo to be telling the truth.

What each method can claim

Capability	Proof of play	In-creative	Proof of Display
Source of evidence	The player's own local log, the device reporting on itself	Measurement code inside the creative, reporting from the player's render	An independent sensor watching the screen from outside the player
What it detects	That content was dispatched and a play event was recorded	That the creative was loaded and rendered in the player's environment	What actually appeared on the glass, matched to the campaign by fingerprint
Independence	Self-attested: the same system that failed is the one reporting the failure	Independent of the operator's log, but still runs inside the player stack	Independent of the player, so it still catches faults the player can't see
Catches a black or frozen screen
Catches wrong input or no signal
Catches physical obstruction
Dispute value with an advertiser	Circumstantial: it's the seller's own record, offered on trust	Stronger than the seller's own log, yet still blind to the physical screen	Evidentiary: a third-party measurement neither side had to take on faith

Which one do you actually need?

Not every screen needs independent verification, and pretending otherwise is how verification gets sold to people who won’t get their money back. The question is what a delivery argument costs you.

Playback logs are enough

Your own content, internal comms, or advertising sold on relationships where nobody has ever asked you to prove a spot. The log answers the questions you actually get asked, and it's already free.

In-creative measurement earns its place

You're the buyer, running one campaign across networks you don't own. You can't fit hardware to somebody else's estate, and you need the same measurement everywhere the creative goes. That's what Vojo Passport is for.

Proof of Display pays for itself

Premium sites, audited buyers, or a rate you're trying to defend. Anywhere you already over-deliver to cover a number you can't prove: that cushion costs more, every flight, than the sensor does once.

Questions people ask

What is proof of play in DOOH?: Proof of play is a playback log generated by the media player itself: a timestamped record that says content was dispatched and, according to the player's own software, played. It's useful operational telemetry, but it is self-attested. It describes what the player believes happened, not what independently happened on the screen.
What is Proof of Display?: Proof of Display is independent, sensor-based verification of what actually appeared on a screen. A separate device (Vojo's Harvester) observes the display itself, fingerprints the content it sees, and matches that fingerprint to the scheduled campaign. It answers a different question: not "did the player try to show this" but "did this actually appear on the glass."
Is proof of play the same as Proof of Display?: No. Proof of play measures the player's intent and internal state; Proof of Display measures the outcome on the screen, independently of the player. A player can log a successful play while the screen is black, showing no signal, or physically obstructed, and proof of play won't catch any of those. Proof of Display will, because it never asks the player to grade its own work.
Why can't proof of play detect a black screen or no signal?: Because most proof-of-play systems log at the software layer: the player confirms it issued a play command, decoded a file, or rendered a frame in its own pipeline. None of that requires the output to have reached a lit, correctly-connected display.
What about creative wrappers and in-creative verification?: A creative wrapper is measurement code that ships inside the creative and reports from within the player's render. It gives the buy side an independent record of the render, but it measures from the same side of the glass as the player, so it complements Proof of Display rather than replacing it. Vojo offers this as Vojo Passport (content-level verification, never called Proof of Display).
Is Proof of Display patented?: Vojo's Proof of Display method is patented, with granted patents in the United Kingdom and the United States, and a European patent application pending.