Understanding Game Development Milestones
Anyone who has spent some time around game development will eventually come across terms like prototype, vertical slice, alpha, beta and gold master.
These terms are often used as if they were clearly defined stages that every game passes through in exactly the same way. In reality, things are a little more complicated.
Different studios use these terms differently and not every project follows the same development process.
Still, the terms are useful because they describe different states of a game and, more importantly, the questions a development team is trying to answer at each point.
Put simply the journey looks something like this:
“Does the idea work?” → “Can we make the game we envision?” → “Is the game complete?” → “Is it stable?” → “Can we release it?”
The prototype usually comes at the beginning of development.
1. The Prototype – Does the Idea Work?
At this point, the goal is not to create a beautiful game. The goal is to find out whether a particular idea actually works.
A prototype can therefore look extremely rough. Placeholder graphics, simple shapes, missing animations, temporary UI and improvised solutions are all perfectly normal.
A developer might want to find out:
- Does the character movement feel good?
- Does the planned combat system work?
- Is a particular gameplay mechanic fun?
- Does the camera behave as expected?
- Is a certain multiplayer concept technically feasible?
The key difference from later stages is this:
A prototype is meant to answer a question – not to represent a finished game.
A prototype can even be deliberately thrown away.
If the team discovers that a particular mechanic simply isn’t fun, the prototype has still been successful. It provided that information early, when changing direction is relatively cheap.
2. The Vertical Slice – What Could the Finished Game Look Like?
Once the basic ideas have been tested the team faces a different question:
Can we actually produce the game at the quality level we are aiming for?
This is where the vertical slice comes in.
A vertical slice is a small but relatively complete section of the game. The term “vertical” essentially means that the slice goes through the different layers of the game rather than representing only one isolated system.
Instead of building an entire open world, for example, the team might create a single small area.
That area could already include:
- final or near-final art
- lighting
- animation
- sound and music
- gameplay
- UI
- enemies
- visual effects
- dialogue
- technical systems
The purpose is to demonstrate what the finished game should look and feel like.
This makes the vertical slice very different from a prototype:
| Prototype | Vertical Slice |
|---|---|
| Tests an idea | Demonstrates the intended quality |
| Can be ugly | Should look close to the target |
| Can focus on one mechanic | Covers many aspects of the game |
| Focuses on learning | Focuses on feasibility and presentation |
| May be thrown away | Often becomes a quality reference |
A vertical slice is therefore not simply a “small prototype.” It is more like a representative cross-section of the intended final product.
3. Alpha – Building the Actual Game
With alpha, the focus shifts again.
While prototypes and vertical slices are primarily about answering questions, alpha is increasingly about actually completing the game.
A commonly used definition is:
Alpha means, roughly speaking, that the major features and content are in place but the game is not finished yet.
There is no universal definition, though. Different studios and projects may define their alpha milestone differently.
During alpha, the team is typically still creating content and finishing major systems. At the same time, quality assurance and testing start to become increasingly important.
Bugs are completely normal at this stage.
There may still be:
- missing or unfinished content
- placeholders
- balance problems
- crashes
- performance issues
- unfinished animations
- technical debt
Another important term often associated with this stage is feature complete.
Feature complete generally means that the major planned gameplay features are implemented and the team does not expect to add significant new systems anymore.
From that point onward, the focus can increasingly shift toward finishing, polishing, and fixing what is already there.
4. Beta – Making the Game Stable
The beta phase is often understood as the stage where the game is largely complete.
The important difference from alpha is not that the game suddenly has no bugs. Instead, the focus changes.
During alpha, teams may still be heavily working on content and functionality.
During beta, the focus is increasingly on:
- bug fixing
- stability
- performance
- balance
- compatibility
- usability
- localization
- extensive testing
Again, there is no universal definition of “beta.”
Some projects have a closed beta involving only selected testers. Others may run an open beta with thousands or even millions of players.
So “beta” does not necessarily mean:
“The game is almost perfect.”
It is closer to:
“The core game is there. Now we need to find out what still doesn’t work.”
5. Gold Master – Ready for Release
At the end of the traditional development process comes the gold master.
The term comes from an era when games were distributed on physical media. The gold master was the final version that was used as the source for manufacturing those copies.
The technology has changed but the term has survived in parts of the industry.
Today, a gold master essentially means:
This version is approved for release.
That does not necessarily mean the game is completely bug-free.
Modern games can receive patches immediately after launch (aka day 1 patch) and in many cases they continue to be updated for years.
The important point is that the version has reached a state where it is considered suitable for release.
The gold master is therefore not simply “the best version of the game.” It is a release milestone.
Comparing the Development Stages
The different terms become easier to understand if we look at the central question behind each stage:
| Stage | The Main Question |
|---|---|
| Prototype | Does the idea work? |
| Vertical Slice | Can we produce the game at the intended quality? |
| Alpha | Is the game largely built? |
| Beta | Is the game stable and reliable? |
| Gold Master | Is this version ready for release? |
This table should not be treated as a strict industry standard.
A small indie game may never create a formal vertical slice. A live-service game may use a completely different set of milestones. Early Access can blur the boundaries between development and release entirely.
The terminology is useful but the actual process depends heavily on the project and the studio.
Why Do These Terms Matter?
The real value of these terms is therefore not putting a game into a particular box.
They help development teams create shared expectations.
If someone says:
“We’re in beta.”
the team should have a rough understanding that this is probably not the time to start developing an entirely new core gameplay system.
Instead, the focus should be on making the existing game stable, performant, balanced, and ready for release.
And if someone says:
“We need a prototype.”
the expectation should not be a polished environment with final art and perfect menus.
The terminology is therefore primarily a communication tool within game development.
A Simplified Development Journey
The entire process can be viewed as a gradual movement from uncertainty toward confidence.
Prototype
→ The idea might work.
Vertical Slice
→ We can demonstrate what the game should look and feel like.
Alpha
→ The major parts of the game are there.
Beta
→ The game is largely complete and is being stabilized.
Gold Master
→ This version is ready to be released.
The important thing to remember is that development is never perfectly linear and not every studio uses these terms in exactly the same way.
So when you hear one of these terms, don’t focus only on the label.
Instead, ask:
„What problem is the team trying to solve at this point?„
That question gets much closer to the real meaning behind prototype, vertical slice, alpha, beta and gold master.