Which Anvil Tools Run Locally and Which Use a Service?

A tool-by-tool account of local processing, file uploads, external services, and suitability for sensitive data.

Tool	Runs locally?	Uploads files?	Uses external service?	Best for sensitive data?	Notes
Background Remover	Yes	No	No	Better than upload-based tools, but review the output and device policy.	A model is loaded in the browser; no Anvil conversion upload.
Base64 Encoder & Decoder	Yes	No	No	Suitable for local text, subject to your device and browser security.	Text-only workflow; encoded text remains readable after decoding.
Color Palette Generator	Yes	No	No	Suitable; the tool processes only color values locally.	Run a separate contrast check before using text/background pairs.
CSV to JSON Converter	Yes	No	No	Suitable for local text, but remove confidential data when a synthetic sample will do.	Values remain strings; validate the receiving schema separately.
Hash Generator	Yes	No	No	Suitable for local text, but hashes can still reveal information about weak inputs.	Text input only; use a dedicated file hash utility for files.
Image to PDF Converter	Yes	No	No	Suitable for local files, subject to your device and browser security.	Review page order, dimensions, and readability before sharing.
JSON Formatter & Validator	Yes	No	No	Suitable for local text, but use synthetic data whenever possible.	Successful formatting proves syntax, not semantic correctness.
JWT Decoder	Yes	No	No	Avoid real bearer tokens; use a synthetic or redacted token.	Inspection is not authentication or signature verification.
Password Generator	Yes	No	No	Suitable for local generation; save the result directly in a trusted password manager.	Use a unique password per account and enable MFA where available.
PDF Merge	Yes	No	No	Suitable for local files, subject to your device and browser security.	Inspect the merged file before relying on forms, signatures, or accessibility.
QR Code Generator	Yes	No	No	Suitable for local generation, but anyone who scans the code can read its payload.	The current UI uses a fixed high error-correction setting.
Temporary Email Generator	No	No	Guerrilla Mail through the Anvil backend	No. Use only non-sensitive test messages.	The tool interface and every inbox, message, loading, error, and generated-address state are ad-free.
Text Case Converter	Yes	No	No	Suitable for local text, subject to your device and browser security.	Review names, acronyms, and code identifiers after conversion.
Text Difference Checker	Yes	No	No	Suitable for local text, subject to your device and browser security.	Treat moved lines as delete/add output and review context manually.
Unit Converter	Yes	No	No	Suitable; numeric inputs are processed locally.	Use authoritative factors and tolerances for regulated decisions.
Unix Timestamp Converter	Yes	No	No	Suitable; timestamp values are processed locally.	Confirm units and use UTC when exchanging system timestamps.
URL Encoder & Decoder	Yes	No	No	Suitable for local text, but do not paste live secrets into examples.	Inspect the final destination and query semantics before use.
User-Agent String Reference	Yes	No	No	Suitable; use only in systems you own or are authorized to test.	Do not use samples to evade access controls or impersonate verified crawlers.
UUID Generator	Yes	No	No	Suitable for generating non-secret identifiers locally.	Do not use a UUID alone as authentication or authorization.
Word & Character Counter	Yes	No	No	Suitable for local text, subject to your device and browser security.	Use the destination platform's rules when a limit is strict.

“Runs locally” describes the tool calculation, not the ordinary network requests used to load the website. Device security, browser extensions, shared computers, backups, and the final destination still matter. Temporary Email is the exception because receiving mail requires the Anvil backend and an external mailbox provider.

Last reviewed: October 11, 2026.