How do I decode a Base64 string online?

Paste your Base64 string into SmartDevBox at smartdevbox.com. It automatically detects Base64 encoding and decodes it instantly — no configuration needed.

How do I decode a JWT token without a secret?

Paste your JWT token into SmartDevBox. The JWT Inspector tool decodes the header and payload and displays them as readable JSON. Note: this decodes but does not verify the signature — you don't need the secret to read the claims.

How do I format or pretty-print JSON?

Paste your minified or unformatted JSON into SmartDevBox. The JSON Formatter tool detects it automatically and pretty-prints it with configurable indentation.

How do I convert a Unix timestamp to a human-readable date?

Paste a Unix timestamp (e.g. 1700000000) into SmartDevBox. The Unix Timestamp converter detects it and shows the equivalent date and time in UTC and your local timezone.

How do I convert JSON to CSV?

Paste a JSON array of objects into SmartDevBox and select the JSON → CSV tool. It converts your data to comma-separated format with headers derived from the JSON keys.

How do I compute a SHA-256 hash online?

Use the Hash Generator tool on SmartDevBox. Paste any text and it computes MD5, SHA-1, SHA-256, and SHA-512 hashes simultaneously in the browser.

How do I parse and understand a cron expression?

Paste your cron expression (e.g. "0 9 * * 1-5") into SmartDevBox. The Cron Job Parser explains it in plain English and shows the next scheduled run times.

How do I decode an X.509 certificate online?

Paste a PEM-encoded certificate (beginning with -----BEGIN CERTIFICATE-----) into SmartDevBox. The Certificate Decoder extracts and displays the subject, issuer, validity dates, public key, and extensions.

Is SmartDevBox free to use?

Yes. SmartDevBox is completely free with no account or sign-up required. All tools run in the browser. An optional AI mode (for ambiguous input detection) can be enabled with your own OpenAI API key.

Does SmartDevBox send my data to a server?

No. All tools run entirely in the browser using client-side JavaScript. Your data never leaves your machine unless you opt into the AI mode, which sends input to OpenAI for format detection.

Text Tools

Text & Code Comparison

Paste two versions of anything. See exactly what changed — additions in green, deletions in red, updated in real time as you type.

The Split Diff Tool

SmartDevBox includes a dedicated Split & Diff panel that lets you compare two blocks of text side by side. The diff updates in real time as you type in either pane — no submit button, no page reload.

The tool uses a line-level Myers diff algorithm — the same approach used by git diff — giving you an accurate and familiar view of changes between any two text versions.

Added linesHighlighted in green

Removed linesHighlighted in red

UnchangedShown in neutral for context

What You Can Compare

JSON objectsSpot added, renamed, or changed fields between two API responses.

SQL queriesReview a query change before deploying.

Config filesYAML, TOML, INI, .env — compare any version.

XML documentsCompare two API payloads or schema versions.

CSS stylesheetsBefore and after a refactor.

JavaScript / TypeScriptCompare two function or module implementations.

Plain textContracts, docs, commit messages, release notes.

Log outputSpot what changed between two runs.

HTML markupCompare two rendered templates.

How to Use It

1Open SmartDevBox.
2In the left sidebar, select Split & Diff under Text — or press ⌘K and type “diff”.
3Paste the original version in the left pane.
4Paste the modified version in the right pane.
5Differences highlight immediately — no button to click.

Combine with Other Tools

A common workflow is to format both inputs before diffing. For example:

1Paste minified JSON — SmartDevBox auto-detects and formats it.
2Copy the formatted output.
3Repeat for the second blob, then diff the two formatted versions.

Because both inputs have consistent indentation, the diff is clean and perfectly line-aligned — no noise from whitespace differences.

Why a Browser-Based Diff Tool?

Opening a desktop diff application or uploading files to a web service adds unnecessary friction during debugging. SmartDevBox's diff tool is zero-friction: open the app, paste, done. No install, no account, and no data uploaded to a server. Both panes stay in the browser.

SmartDevBox Diff vs Standalone Diff Tools

Dedicated diff tools like diff, vimdiff, and web services like diffchecker.com all work well in isolation. SmartDevBox's diff tool is distinguished by its integration with the rest of the toolbox:

Isolated diff toolsCompare plain text only. To diff formatted JSON you must format it yourself first, in a separate tool or editor.

SmartDevBox diffAuto-format JSON, XML, or SQL in the same app, then switch to Split & Diff. No copy-pasting between tools or browser tabs.

For JSON comparison in particular, a recommended workflow is: paste into the main input area to auto-format, copy the formatted output, then open Split & Diff and compare the two formatted versions. The diff is clean because consistent indentation eliminates whitespace noise.

diffchecker.com and similar services upload your text to their servers. SmartDevBox's diff runs entirely in the browser — nothing is uploaded, making it safe for internal code, credentials, and API responses.

Frequently Asked Questions

Is the diff line-level or character-level?

The primary view is line-level, like git diff. Within changed lines, intra-line character differences are also highlighted to help you spot small changes like a renamed key or a changed value.

Is there a size limit?

No hard limit — the diff runs client-side, limited only by your browser's available memory. Typical development payloads up to a few thousand lines compare instantly.

Does the diff tool send my text anywhere?

No. Both panes are processed entirely in the browser. See the Privacy & Security page for full details.