depends_on reads fine when a Compose file has two or three services. Past that, tracing who starts after whom means scrolling between blocks and holding the chain in your head. docker compose alpha viz reads the same file and prints the graph instead.
docker compose alpha viz
What it prints
Against a two-service file (web depending on db), the default output is a minimal Graphviz digraph:
digraph "myapp" {
layout=dot;
"db" [style="filled" label=<<font point-size="15">db</font>>];
"web" [style="filled" label=<<font point-size="15">web</font>>];
"web" -> "db";
}
Add --image, --ports, and --networks and each node’s label grows to match:
"web" [style="filled" label=<<font point-size="15">web</font><font point-size="10"><br/><br/><b>Networks:</b><br/>backend<br/>frontend</font><font point-size="10"><br/><br/><b>Ports:</b><br/>8080:80 (tcp, ingress)</font><font point-size="10"><br/><br/><b>Image:</b><br/>nginx:alpine</font>>];
Piped through dot -Tpng, that same output renders as:
--spaces swaps the default tab indentation for spaces, and --indentation-size sets how many, which matters if you’re diffing the output in version control rather than just reading it once.
Why it matters
The output is plain DOT, the input format Graphviz has read since long before Compose existed. With Graphviz installed, docker compose alpha viz | dot -Tpng -o graph.png turns any Compose file into a picture in one line, no need to hand-draw the dependency chain to explain a stack in a review or an onboarding doc. It reads the same depends_on graph Compose itself uses to decide startup order, so the picture and the actual behavior can’t drift apart the way a hand-maintained diagram would.
Pro tip: alpha doesn’t come with a graduation timer
viz is the other command living under docker compose alpha alongside generate, and the same rules from Tip #85 apply: flag names and output format can change release to release, with no deprecation notice. viz first landed in April 2023, generate in October 2024. Unlike watch, which spent a year under alpha before graduating, neither has moved yet. Alpha status describes stability guarantees, not how long a command has been around.
If you’re the kind of reader who read Tip #88 and went looking through pkg/compose/ in the Compose source, viz’s implementation is a short, self-contained file, a good second one to read after generate’s.