{"id":1082,"date":"2026-08-17T00:30:15","date_gmt":"2026-08-17T00:30:15","guid":{"rendered":"https:\/\/www.devopsschool.com\/tutorials\/?p=1082"},"modified":"2026-08-17T00:30:16","modified_gmt":"2026-08-17T00:30:16","slug":"go-tutorial-exported-and-unexported-identifiers","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/tutorials\/go-tutorial-exported-and-unexported-identifiers\/","title":{"rendered":"Go Tutorial: Exported and Unexported Identifiers"},"content":{"rendered":"\n

This concept becomes much easier once you remember one rule<\/strong>:<\/p>\n\n\n\n

\n

Starts with an uppercase letter \u2192 Exported<\/strong>
Starts with a lowercase letter \u2192 Unexported<\/strong><\/p>\n<\/blockquote>\n\n\n\n

In Go, this is how you control whether something can be accessed from another package.<\/p>\n\n\n\n

\n\n\n\n

1. First: What is an identifier?<\/h2>\n\n\n\n

An identifier<\/strong> is simply a name you give to something in Go.<\/p>\n\n\n\n

Examples:<\/p>\n\n\n\n

var age int\n\nfunc PrintMessage() {}\n\ntype User struct {}\n\nconst MaxUsers = 100<\/code><\/pre>\n\n\n\n
Here, these are identifiers:<\/p>\n\n\n\n
age\nPrintMessage\nUser\nMaxUsers<\/code><\/pre>\n\n\n\n
Go uses the first letter<\/strong> of an identifier to decide whether other packages can access it.<\/p>\n\n\n\n
\n\n\n\n
2. Exported vs Unexported<\/h1>\n\n\n\n
Feature<\/th>Exported<\/th>Unexported<\/th><\/tr><\/thead>
First letter<\/td>Uppercase<\/td>Lowercase<\/td><\/tr>
Example function<\/td>PrintMessage()<\/code><\/td>printMessage()<\/code><\/td><\/tr>
Example variable<\/td>Username<\/code><\/td>username<\/code><\/td><\/tr>
Example type<\/td>User<\/code><\/td>user<\/code><\/td><\/tr>
Example struct field<\/td>Name<\/code><\/td>name<\/code><\/td><\/tr>
Accessible inside same package<\/td>\u2705 Yes<\/td>\u2705 Yes<\/td><\/tr>
Accessible from another package<\/td>\u2705 Yes<\/td>\u274c No<\/td><\/tr>
Similar idea in other languages<\/td>Public<\/td>Private-ish<\/td><\/tr>
Main purpose<\/td>Public package API<\/td>Internal implementation<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
The easiest mental model is:<\/p>\n\n\n\n
Uppercase = package exposes it\nLowercase = package keeps it internal<\/code><\/pre>\n\n\n\n
\n\n\n\n
3. WHAT is an exported identifier?<\/h1>\n\n\n\n
An exported identifier is something that another Go package is allowed to access<\/strong>.<\/p>\n\n\n\n
For example:<\/p>\n\n\n\n
func SayHello() {\n    fmt.Println(\"Hello\")\n}<\/code><\/pre>\n\n\n\n
Because SayHello<\/code> begins with uppercase S<\/code>, another package can use:<\/p>\n\n\n\n
greeting.SayHello()<\/code><\/pre>\n\n\n\n
\n\n\n\n
4. WHAT is an unexported identifier?<\/h1>\n\n\n\n
An unexported identifier can normally only be used inside the package where it was declared<\/strong>.<\/p>\n\n\n\n
For example:<\/p>\n\n\n\n
func buildMessage() {\n    fmt.Println(\"Building message\")\n}<\/code><\/pre>\n\n\n\n
Because buildMessage<\/code> begins with lowercase b<\/code>, another package cannot do:<\/p>\n\n\n\n
greeting.buildMessage()<\/code><\/pre>\n\n\n\n
That would produce a compile error.<\/p>\n\n\n\n
\n\n\n\n
5. WHY does Go have this?<\/h1>\n\n\n\n
Packages need a way to separate:<\/p>\n\n\n\n
Things users should use\n\nfrom\n\nThings used internally by the package<\/code><\/pre>\n\n\n\n
Imagine a package like this:<\/p>\n\n\n\n
greeting\n\u2502\n\u251c\u2500\u2500 SayHello()        \u2190 users should call this\n\u251c\u2500\u2500 NewGreeting()     \u2190 users should call this\n\u2502\n\u251c\u2500\u2500 buildMessage()    \u2190 internal helper\n\u2514\u2500\u2500 validateName()    \u2190 internal helper<\/code><\/pre>\n\n\n\n
There is usually no reason for users of the package to know about internal functions such as buildMessage()<\/code>.<\/p>\n\n\n\n
Go therefore lets the package expose only its intended API.<\/p>\n\n\n\n
\n\n\n\n
6. HOW does Go decide?<\/h1>\n\n\n\n
The rule is extremely simple.<\/p>\n\n\n\n
flowchart TD\n    A[Identifier] --> B{First letter uppercase?}\n    B -->|Yes| C[Exported]\n    B -->|No| D[Unexported]\n\n    C --> E[Other packages can access it]\n    D --> F[Other packages cannot access it]<\/code><\/pre>\n\n\n\n
For example:<\/p>\n\n\n\n
User\nPrint\nMaxConnections\nName<\/code><\/pre>\n\n\n\n
are exported.<\/p>\n\n\n\n
But:<\/p>\n\n\n\n
user\nprint\nmaxConnections\nname<\/code><\/pre>\n\n\n\n
are unexported.<\/p>\n\n\n\n
\n\n\n\n
7. Complete Self-Contained Example<\/h1>\n\n\n\n
Because exported\/unexported identifiers are mainly about communication between packages<\/strong>, the best example needs two packages.<\/p>\n\n\n\n
We will create this tiny project:<\/p>\n\n\n\n
exportdemo\/\n\u2502\n\u251c\u2500\u2500 go.mod\n\u251c\u2500\u2500 main.go\n\u2502\n\u2514\u2500\u2500 greeting\/\n    \u2514\u2500\u2500 greeting.go<\/code><\/pre>\n\n\n\n
\n\n\n\n
Step 1: go.mod<\/code><\/h2>\n\n\n\n
Create:<\/p>\n\n\n\n
go.mod<\/code><\/pre>\n\n\n\n
with:<\/p>\n\n\n\n
module example.com\/exportdemo\n\ngo 1.22<\/code><\/pre>\n\n\n\n
This simply gives our Go project a module name.<\/p>\n\n\n\n
\n\n\n\n
Step 2: greeting\/greeting.go<\/code><\/h2>\n\n\n\n
Create a directory named:<\/p>\n\n\n\n
greeting<\/code><\/pre>\n\n\n\n
Inside it create:<\/p>\n\n\n\n
greeting.go<\/code><\/pre>\n\n\n\n
with:<\/p>\n\n\n\n
package greeting\n\n\/\/ Message is exported because it starts with uppercase M.\n\/\/ Other packages can access it.\nvar Message = \"Hello from the greeting package\"\n\n\/\/ secretMessage is unexported because it starts with lowercase s.\n\/\/ Only code inside package greeting can access it.\nvar secretMessage = \"This is a secret message\"\n\n\/\/ SayHello is exported because it starts with uppercase S.\n\/\/ Other packages can call it.\nfunc SayHello() string {\n\treturn secretMessage\n}\n\n\/\/ buildMessage is unexported because it starts with lowercase b.\n\/\/ Only code inside package greeting can call it.\nfunc buildMessage() string {\n\treturn \"Message created internally\"\n}<\/code><\/pre>\n\n\n\n
Notice something important here.<\/p>\n\n\n\n
SayHello()<\/code> can access:<\/p>\n\n\n\n
secretMessage<\/code><\/pre>\n\n\n\n
even though secretMessage<\/code> is unexported.<\/p>\n\n\n\n
Why?<\/p>\n\n\n\n
Because both are inside:<\/p>\n\n\n\n
package greeting<\/code><\/pre>\n\n\n\n
Unexported does not<\/strong> mean:<\/p>\n\n\n\n
only this function can access it<\/code><\/pre>\n\n\n\n
It means:<\/p>\n\n\n\n
only this package can access it<\/code><\/pre>\n\n\n\n
\n\n\n\n
8. main.go<\/code><\/h1>\n\n\n\n
Create:<\/p>\n\n\n\n
main.go<\/code><\/pre>\n\n\n\n
with:<\/p>\n\n\n\n
package main\n\nimport (\n\t\"fmt\"\n\n\t\"example.com\/exportdemo\/greeting\"\n)\n\nfunc main() {\n\n\t\/\/ Message starts with uppercase M.\n\t\/\/ Therefore it is exported from package greeting.\n\tfmt.Println(greeting.Message)\n\n\t\/\/ SayHello starts with uppercase S.\n\t\/\/ Therefore we can call it from package main.\n\tfmt.Println(greeting.SayHello())\n\n\t\/\/ The following DOES NOT work because secretMessage\n\t\/\/ starts with lowercase s.\n\t\/\/\n\t\/\/ fmt.Println(greeting.secretMessage)\n\n\t\/\/ This also DOES NOT work because buildMessage\n\t\/\/ starts with lowercase b.\n\t\/\/\n\t\/\/ fmt.Println(greeting.buildMessage())\n}<\/code><\/pre>\n\n\n\n
\n\n\n\n
9. Run the program<\/h1>\n\n\n\n
From the exportdemo<\/code> directory:<\/p>\n\n\n\n
go run .<\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
Hello from the greeting package\nThis is a secret message<\/code><\/pre>\n\n\n\n
\n\n\n\n
10. What exactly happened?<\/h1>\n\n\n\n
Our program has two packages:<\/p>\n\n\n\n
main\ngreeting<\/code><\/pre>\n\n\n\n
Inside greeting<\/code> we declared:<\/p>\n\n\n\n
Message\nsecretMessage\nSayHello\nbuildMessage<\/code><\/pre>\n\n\n\n
Their visibility is:<\/p>\n\n\n\n
Identifier<\/th>Starts With<\/th>Exported?<\/th>Accessible from main<\/code>?<\/th><\/tr><\/thead>
Message<\/code><\/td>M<\/code> uppercase<\/td>\u2705<\/td>\u2705<\/td><\/tr>
secretMessage<\/code><\/td>s<\/code> lowercase<\/td>\u274c<\/td>\u274c<\/td><\/tr>
SayHello<\/code><\/td>S<\/code> uppercase<\/td>\u2705<\/td>\u2705<\/td><\/tr>
buildMessage<\/code><\/td>b<\/code> lowercase<\/td>\u274c<\/td>\u274c<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
So this works:<\/p>\n\n\n\n
greeting.Message<\/code><\/pre>\n\n\n\n
and this works:<\/p>\n\n\n\n
greeting.SayHello()<\/code><\/pre>\n\n\n\n
But this doesn’t:<\/p>\n\n\n\n
greeting.secretMessage<\/code><\/pre>\n\n\n\n
and this doesn’t:<\/p>\n\n\n\n
greeting.buildMessage()<\/code><\/pre>\n\n\n\n
\n\n\n\n
11. An important point: unexported does NOT mean inaccessible everywhere<\/h1>\n\n\n\n
Suppose we have:<\/p>\n\n\n\n
package greeting\n\nvar secretMessage = \"Secret\"\n\nfunc SayHello() string {\n\treturn secretMessage\n}<\/code><\/pre>\n\n\n\n
This is perfectly valid.<\/p>\n\n\n\n
SayHello()<\/code> and secretMessage<\/code> belong to the same package<\/strong>.<\/p>\n\n\n\n
Therefore:<\/p>\n\n\n\n
SayHello()<\/code><\/pre>\n\n\n\n
can use:<\/p>\n\n\n\n
secretMessage<\/code><\/pre>\n\n\n\n
The restriction only becomes important when another package tries to access it.<\/p>\n\n\n\n
Think of the package as a house:<\/p>\n\n\n\n
Package greeting\n\u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n\u2502                              \u2502\n\u2502  Message       \u2190 exported    \u2502\n\u2502  SayHello()    \u2190 exported    \u2502\n\u2502                              \u2502\n\u2502  secretMessage \u2190 internal    \u2502\n\u2502  buildMessage  \u2190 internal    \u2502\n\u2502                              \u2502\n\u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n        \u2191\n        \u2502\n Package main can only\n access exported names<\/code><\/pre>\n\n\n\n
\n\n\n\n
12. Struct fields follow the same rule<\/h1>\n\n\n\n
This rule is not limited to functions.<\/p>\n\n\n\n
Consider:<\/p>\n\n\n\n
type User struct {\n\tName string\n\tage  int\n}<\/code><\/pre>\n\n\n\n
Here:<\/p>\n\n\n\n
Name<\/code><\/pre>\n\n\n\n
is exported.<\/p>\n\n\n\n
But:<\/p>\n\n\n\n
age<\/code><\/pre>\n\n\n\n
is unexported.<\/p>\n\n\n\n
Therefore another package can do:<\/p>\n\n\n\n
user.Name<\/code><\/pre>\n\n\n\n
but cannot do:<\/p>\n\n\n\n
user.age<\/code><\/pre>\n\n\n\n
Again:<\/p>\n\n\n\n
Name \u2192 uppercase \u2192 exported\nage  \u2192 lowercase \u2192 unexported<\/code><\/pre>\n\n\n\n
\n\n\n\n
13. Functions follow the same rule<\/h1>\n\n\n\n
func StartServer() {}<\/code><\/pre>\n\n\n\n
Exported:<\/p>\n\n\n\n
StartServer\n\u2191\nuppercase<\/code><\/pre>\n\n\n\n
Another package can call it.<\/p>\n\n\n\n
But:<\/p>\n\n\n\n
func startServer() {}<\/code><\/pre>\n\n\n\n
is unexported.<\/p>\n\n\n\n
\n\n\n\n
14. Types follow the same rule<\/h1>\n\n\n\n
Exported:<\/p>\n\n\n\n
type User struct{}<\/code><\/pre>\n\n\n\n
Unexported:<\/p>\n\n\n\n
type user struct{}<\/code><\/pre>\n\n\n\n
\n\n\n\n
15. Constants and variables follow the same rule<\/h1>\n\n\n\n
Exported:<\/p>\n\n\n\n
const MaxUsers = 100\n\nvar ServerName = \"production\"<\/code><\/pre>\n\n\n\n
Unexported:<\/p>\n\n\n\n
const maxUsers = 100\n\nvar serverName = \"production\"<\/code><\/pre>\n\n\n\n
\n\n\n\n
16. Methods follow the same rule<\/h1>\n\n\n\n
Exported:<\/p>\n\n\n\n
func (u User) PrintName() {\n}<\/code><\/pre>\n\n\n\n
Unexported:<\/p>\n\n\n\n
func (u User) printName() {\n}<\/code><\/pre>\n\n\n\n
\n\n\n\n
17. One rule applies everywhere<\/h1>\n\n\n\n
You do not<\/strong> need separate rules for variables, functions, structs, methods, and constants.<\/p>\n\n\n\n
Remember this:<\/p>\n\n\n\n
Code<\/th>Exported?<\/th><\/tr><\/thead>
User<\/code><\/td>\u2705<\/td><\/tr>
user<\/code><\/td>\u274c<\/td><\/tr>
Print()<\/code><\/td>\u2705<\/td><\/tr>
print()<\/code><\/td>\u274c<\/td><\/tr>
Name<\/code><\/td>\u2705<\/td><\/tr>
name<\/code><\/td>\u274c<\/td><\/tr>
MaxSize<\/code><\/td>\u2705<\/td><\/tr>
maxSize<\/code><\/td>\u274c<\/td><\/tr>
Connect()<\/code><\/td>\u2705<\/td><\/tr>
connect()<\/code><\/td>\u274c<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n\n\n
18. WHEN should you export something?<\/h1>\n\n\n\n
Export something when users of your package are supposed to use it.<\/p>\n\n\n\n
For example:<\/p>\n\n\n\n
package database\n\nfunc Connect() {\n}<\/code><\/pre>\n\n\n\n
If another package needs to connect to the database:<\/p>\n\n\n\n
database.Connect()<\/code><\/pre>\n\n\n\n
then Connect<\/code> needs to be exported.<\/p>\n\n\n\n
\n\n\n\n
19. WHEN should you keep something unexported?<\/h1>\n\n\n\n
Use lowercase names for implementation details.<\/p>\n\n\n\n
For example:<\/p>\n\n\n\n
package database\n\nfunc Connect() {\n\tvalidateConfig()\n\topenConnection()\n}\n\nfunc validateConfig() {\n}\n\nfunc openConnection() {\n}<\/code><\/pre>\n\n\n\n
Other packages only need:<\/p>\n\n\n\n
database.Connect()<\/code><\/pre>\n\n\n\n
They don’t need:<\/p>\n\n\n\n
validateConfig()\nopenConnection()<\/code><\/pre>\n\n\n\n
So those helpers remain unexported.<\/p>\n\n\n\n
This gives you a clean package API.<\/p>\n\n\n\n
\n\n\n\n
20. WHERE will you see this in real Go programs?<\/h1>\n\n\n\n
Very frequently.<\/p>\n\n\n\n
Consider the standard fmt<\/code> package.<\/p>\n\n\n\n
You write:<\/p>\n\n\n\n
fmt.Println(\"Hello\")<\/code><\/pre>\n\n\n\n
Notice:<\/p>\n\n\n\n
Println\nP\n\u2191\nuppercase<\/code><\/pre>\n\n\n\n
Println<\/code> is exported by the fmt<\/code> package.<\/p>\n\n\n\n
Similarly:<\/p>\n\n\n\n
http.ListenAndServe(...)<\/code><\/pre>\n\n\n\n
ListenAndServe<\/code> begins with uppercase L<\/code>, so the net\/http<\/code> package exposes it.<\/p>\n\n\n\n
This naming convention is fundamental to how Go packages work.<\/p>\n\n\n\n
\n\n\n\n
21. One subtle point: main<\/code> is lowercase<\/h1>\n\n\n\n
You may wonder:<\/p>\n\n\n\n
func main() {\n}<\/code><\/pre>\n\n\n\n
Why isn’t it:<\/p>\n\n\n\n
func Main() {\n}<\/code><\/pre>\n\n\n\n
main()<\/code> is special.<\/p>\n\n\n\n
Go specifically looks for:<\/p>\n\n\n\n
package main\n\nfunc main()<\/code><\/pre>\n\n\n\n
as the program’s entry point.<\/p>\n\n\n\n
It isn’t designed to be exported and called by other packages.<\/p>\n\n\n\n
So:<\/p>\n\n\n\n
main<\/code><\/pre>\n\n\n\n
being lowercase is intentional.<\/p>\n\n\n\n
\n\n\n\n
22. Exported is similar to public<\/code><\/h1>\n\n\n\n
If you know languages such as Java, C#, C++, or TypeScript, you can roughly think:<\/p>\n\n\n\n
Go                         Java-like idea\n\nSayHello()      \u2248          public\nsayHello()      \u2248          package internal<\/code><\/pre>\n\n\n\n
But Go does not<\/strong> require keywords such as:<\/p>\n\n\n\n
public\nprivate\nprotected<\/code><\/pre>\n\n\n\n
Instead, Go uses naming.<\/p>\n\n\n\n
Java-style idea:<\/p>\n\n\n\n
public void SayHello() {\n}<\/code><\/pre>\n\n\n\n
Go:<\/p>\n\n\n\n
func SayHello() {\n}<\/code><\/pre>\n\n\n\n
The uppercase S<\/code> does the job.<\/p>\n\n\n\n
\n\n\n\n
23. Final Comparison<\/h1>\n\n\n\n
Question<\/th>Exported<\/th>Unexported<\/th><\/tr><\/thead>
What?<\/td>Visible outside package<\/td>Hidden from other packages<\/td><\/tr>
How?<\/td>First letter uppercase<\/td>First letter lowercase<\/td><\/tr>
Why?<\/td>Create public package API<\/td>Hide implementation details<\/td><\/tr>
When?<\/td>Other packages need it<\/td>Only your package needs it<\/td><\/tr>
Where?<\/td>Functions, types, fields, methods, variables, constants<\/td>Same<\/td><\/tr>
Example<\/td>Connect()<\/code><\/td>connect()<\/code><\/td><\/tr>
Other package can use?<\/td>\u2705 Yes<\/td>\u274c No<\/td><\/tr>
Same package can use?<\/td>\u2705 Yes<\/td>\u2705 Yes<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n\n\n
24. The 10-second rule to remember<\/h1>\n\n\n\n
Whenever you see:<\/p>\n\n\n\n
greeting.SayHello()<\/code><\/pre>\n\n\n\n
ask:<\/p>\n\n\n\n
\n
Does SayHello<\/code> start with an uppercase letter?<\/p>\n<\/blockquote>\n\n\n\n
Yes:<\/p>\n\n\n\n
SayHello\n\u2191\nS<\/code><\/pre>\n\n\n\n
Therefore it is exported.<\/p>\n\n\n\n
Whenever you see:<\/p>\n\n\n\n
sayHello<\/code><\/pre>\n\n\n\n
lowercase:<\/p>\n\n\n\n
sayHello\n\u2191\ns<\/code><\/pre>\n\n\n\n
Therefore it is unexported.<\/p>\n\n\n\n
So remember:<\/p>\n\n\n\n
Uppercase \u2192 Exported   \u2192 Other packages can use it\n\nlowercase \u2192 unexported \u2192 Only its package can use it<\/code><\/pre>\n\n\n\n
That single rule will handle almost every beginner-level exported\/unexported identifier question you encounter in Go.<\/p>\n","protected":false},"excerpt":{"rendered":"
This concept becomes much easier once you remember one rule: Starts with an uppercase letter \u2192 ExportedStarts with a lowercase letter \u2192 Unexported In Go, this is… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1082","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts\/1082","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/comments?post=1082"}],"version-history":[{"count":1,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts\/1082\/revisions"}],"predecessor-version":[{"id":1083,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/posts\/1082\/revisions\/1083"}],"wp:attachment":[{"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/media?parent=1082"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/categories?post=1082"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.devopsschool.com\/tutorials\/wp-json\/wp\/v2\/tags?post=1082"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}