Does it work without permission?

Writing usually does (within a user gesture). Reading often requires explicit user permission and is gated by document focus — the browser may prompt the first time.

Why might reading fail?

The document needs focus, the user must have granted clipboard-read permission, and the page must be served over HTTPS (or localhost). Errors are surfaced live.

On browsers that support the async Clipboard read API with image types — yes. Older browsers will only return text.

Is clipboard content sent anywhere?

No. The tool only reads and writes your local clipboard inside the browser; nothing is transmitted.

navigator.clipboard · read · write · images · local

Test your browser clipboard API

Try writing text and reading back text or images from the system clipboard. Works on HTTPS or localhost in modern browsers.

Clipboard Tester

API

missing

navigator.clipboard

Text

—

chars read

Image

—

blob

Status

idle

live

input · write payload

Text to write

Reading the clipboard requires user permission and a focused tab. Writing usually works on user-initiated clicks. Image read needs Clipboard async API support.

output · read result

Press Read or Write to test.

Quick Start

How to test the clipboard API

Modern browsers expose navigator.clipboard for both reading and writing. Both require a secure origin (HTTPS or localhost) and an active user gesture.

01
Write text
Click Write to push the text box contents onto the clipboard.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
writeinpututf-8client-sidevalidated
write · texttext · set
```
Hello!
```
loaded · parsedclient-side
02
Read clipboard
Click Read to pull back whatever is currently copied.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
readoptionslivememoisedtoggles
read · memoiseddata · live
```
text/plain · image/png
```
options set · memoisedlive
03
Image support
Copy an image elsewhere, then Read — image MIME types render inline.
Randomness — where used — comes from crypto.getRandomValues, never Math.random. Heavy work sits in useMemo.
imgcomputeinstantlocaldeterministic
image · instantblob · computed
```
<img blob>
```
computed · instantinstant
04
Diagnose errors
If a step fails, the status banner explains why (HTTPS, focus, permission).
Copy writes through navigator.clipboard and downloads use a Blob — zero network traffic. Same input plus same options always yield the same bytes.
debugcopydownloadzero-networkreproducible
ok · copiedready · copied
```
OK
```
shipped · ready to shipsuccess

Pro tips

Pro tips for everyday utilities

Reach for crypto.getRandomValues

Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.

Sort IDs lexicographically

UUID v4 has no time ordering. Use ULID or UUID v7 if you need sorted IDs.

Mock data with seeds

Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.

Reference cards beat memory

Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.

Browser APIs vary

Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.

Persist in the right place

localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.

Use Cases

When to test the clipboard

Copy buttons, paste flows, debugging permissions.

Verify copy buttons

Make sure your custom Copy button actually wrote to the clipboard. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.

CSPRNG-backed

Paste flows

Confirm rich content survives the round trip. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.

reproducible

Permission audit

See whether Safari, Chrome and Firefox grant read access. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.

snappy

MIME debugging

Inspect which MIME types your clipboard currently holds. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.

feature-detected

Reproduce bugs

Provide a deterministic clipboard state for a flaky test. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.

deterministic

Cross-OS support

Compare clipboard behaviour across Windows, macOS, Linux. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.

production-ready

FAQ

Frequently asked questions

Why does Read fail without a click?

Browsers require a recent user gesture before granting clipboard access. Refresh the page and click Read in one motion.

Does this work on HTTP?

No — the API is restricted to secure origins (HTTPS or localhost) for safety.

Can it read passwords?

Anything currently copied to the system clipboard. Be mindful — close the tab when done.

Why is the image blank?

Some sources copy as text/html only. Try copying directly from an image viewer.

Is anything sent to a server?

No. Clipboard reads and writes happen entirely in your browser.

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