String Template Tester — Live Preview and Debug Variable Injection
Test string templates with real variable values across 7 syntax styles: JS ${var}, Python {var}, Mustache {{var}}, printf %s, Shell $var, Ruby #{var}, and Windows batch %var%. Paste your template, enter variables, and see the rendered output instantly.
How to Use String Template Tester — Live Preview and Debug Variable Injection
How to Use the String Template Tester:
Step 1: Choose a Syntax
Click one of the 8 syntax buttons to select how your template is written:
- Auto — The tool scans your template and detects the syntax automatically. Best for quick testing.
- JS ${var} — JavaScript / TypeScript template literal syntax:
${variableName} - Python {var} — Python
str.format()or f-string style:{variableName} - {{var}} — Mustache / Handlebars style:
{{variableName}} - Printf %s — C-style positional format specifiers:
%s(string),%d(integer),%f(float) - Shell $var — Bash / Shell variable syntax:
$VARIABLE_NAME - Ruby #{var} — Ruby string interpolation:
#{variableName} - Batch %var% — Windows batch / environment variable syntax:
%VARIABLE_NAME%
Step 2: Enter Your Template
Paste or type the template string in the left textarea. The template can span multiple lines and contain any mix of literal text and placeholders.
Examples by syntax:
- JS:
Hello, ${name}! You have ${count} messages. - Python:
Dear {firstName} {lastName}, your invoice is due on {dueDate}. - Mustache:
{{greeting}}, {{name}}! Your score: {{score}} - Printf:
INSERT INTO %s (name, age) VALUES ('%s', %d) - Shell:
export PATH=$HOME/bin:$PATH
Step 3: Enter Variables
In the right textarea, enter your test values:
For named syntaxes (JS, Python, Mustache, Shell, Ruby, Windows):
Enter one variable per line as key=value. The key must match the placeholder name exactly (case-sensitive).
name=Alice
count=5
folder=Inbox
For printf (positional): Enter one value per line in the order they appear in the template:
users
42
1
Lines starting with # are treated as comments and ignored.
Step 4: Read the Output
The rendered output appears in the card below as you type. If any placeholders could not be resolved, a warning banner lists the missing variable names. Unresolved placeholders are left in their original form so you can see exactly what was not substituted.
Step 5: Copy
Click Copy Output to copy the rendered string to your clipboard.
Tips
- Use the example buttons (JS, Python, Mustache, Printf, Shell) to load pre-built templates and see how each syntax works.
- Auto-detect scans for the most specific pattern first:
${...}before$name,{{...}}before{...}. - For Shell templates containing
$HOMEalongside${CUSTOM}, use the explicit JS ${var} mode to avoid ambiguity. - Variable values preserve exact whitespace — do not add extra spaces after the
=sign unless you want them in the output.
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