How is this different from the strict-ASCII checks in the other ASCII category converters?

Every converter in this category (like ASCII to Hex Converter) validates its input and stops at the very first non-ASCII character it hits, since converting further would be meaningless. This tool is the exception: it keeps scanning the whole input and lists every single offending character it finds, which is exactly what you want when auditing a large block of text for stray characters rather than converting it.

What does a passing result tell me?

That every character in your input is within the 0-127 ASCII range, plus the total character count, so you know exactly how much text was checked.

What counts as strict ASCII here?

Code points 0 through 127 only: standard English letters, digits, punctuation, and the C0 control characters. Extended (8-bit) characters, accented letters, smart quotes, em dashes, emoji, and any other code point above 127 are flagged.

Why would smart quotes or an em dash show up as invalid?

Word processors and some chat apps silently substitute "curly" quotes (‘’“”) and an em dash (—) for their plain ASCII equivalents. Those substitutes sit outside the 0-127 range, so pasted text that looks perfectly plain can still fail validation.

ASCII Validator - Find Every Non-ASCII Character Online

Overview

Introduction

Before feeding text into a system that only understands 7-bit ASCII, a legacy protocol, an embedded device, a fixed-width serial format, it helps to know exactly which characters, if any, would break that assumption.

This tool scans a whole block of text in one pass and lists every character outside the 0-127 ASCII range, instead of stopping at the first problem the way a converter's validation step would.

What Is ASCII Validator?

A strict 7-bit ASCII auditor: it walks every character in your input and reports each one whose code point exceeds 127, along with that character's position and exact code point.

It's the one tool in this category built for auditing, not converting, everything else here validates as a side effect of transforming your text and gives up at the first bad character.

How ASCII Validator Works

The input is split into individual characters by Unicode code point (so multi-unit characters like emoji are handled as one logical character rather than mangled surrogate halves), then every character's code point is checked against the 0-127 range.

Passing characters are simply counted; each failing character is recorded with its 1-based position and code point (decimal and hex), and the full list is reported together at the end.

When To Use ASCII Validator

Use it to sanity-check a large paste, a config file's contents, or a data export before sending it somewhere that only accepts strict ASCII.

It's especially useful for finding "invisible" problem characters, smart quotes, non-breaking spaces, zero-width characters, that look identical to their ASCII equivalents on screen.

Often used alongside ASCII Sum Finder, ASCII Length Finder and ASCII Debugger.

Features

Advantages

Reports every offending character in one pass instead of forcing you to fix-and-rerun repeatedly to find them one at a time.
Gives an exact position and code point for each issue, so you can jump straight to the problem in your source text.
Reports the total character count on success, useful as a quick sanity check on its own.

Limitations

Only flags characters; it doesn't attempt to fix or strip them, pair it with a transliteration or removal tool if you need the text made ASCII-safe.
Very large inputs produce a correspondingly long issue list, which can be unwieldy to read through if the text is mostly non-ASCII.

Examples

Clean ASCII input

Input

Hello, World! 123

Output

Valid strict ASCII. 17 characters checked, 0 issues found.

Every character falls within 0-127, so the tool reports the pass and the total character count.

Text with multiple non-ASCII characters

Input

Café — naïve

Output

Invalid: 3 non-ASCII characters found out of 12 total.

Position 4: "é" — code point 233 (0x00E9)
Position 6: "—" — code point 8212 (0x2014)
Position 10: "ï" — code point 239 (0x00EF)

All three non-ASCII characters are listed together, each with its own position and code point, instead of the scan stopping at the first one.

Best Practices & Notes

Best Practices

Run this before a strict-ASCII converter in this category if you're not sure your text is clean, it's faster to see every problem at once than to discover them one rejection at a time.
Watch for smart quotes and em dashes specifically, they're the most common source of surprise failures in text copied from word processors.

Developer Notes

Unlike the shared `validateStrictAscii` helper (which returns on the first non-ASCII character, matching every converter's fail-fast behavior), this tool's logic scans the full `Array.from(input)` character list unconditionally and accumulates every offending character into a list before returning, since reporting everything at once is this tool's entire purpose.

ASCII Validator Use Cases

Auditing a config file or data export before sending it to a system that only accepts 7-bit ASCII
Finding stray smart quotes, em dashes, or non-breaking spaces introduced by pasting from a word processor
Verifying test fixtures or sample data are genuinely ASCII-only before checking them into a repository

Common Mistakes

Assuming plain-looking text is ASCII; curly quotes, em dashes, and non-breaking spaces are common invisible offenders.
Expecting this tool to fix the text; it only reports problems, use a transliteration or find-and-replace tool to actually resolve them.

Tips

If the issue list is long, search your source text for the most common offenders first: curly quotes, em dashes, and non-breaking spaces.
Copy the character count from a passing result to double-check it matches what you expect for your input.

ASCII Validator