I replaced my laptop in March and did the thing everyone threatens to do: no backup restore, fresh install, add software only when I genuinely miss it.
Four months later, an entire category never came back. The one-job utilities — JSON prettifier, diff GUI, hash tool, the little menu-bar timestamp thing — are browser tabs now. Not web apps that ship my data to a server. Client-side pages: they load once, run entirely in the tab, and keep working when the Wi-Fi drops.
That distinction is the whole point. Half of what I paste into these tools is production-adjacent — webhook payloads with customer emails, staging configs, API responses. So my filter is blunt: open DevTools, watch the Network tab while I paste, and close the tab forever if anything leaves. Everything below passes. Fair warning: the tool links here point at fewly, which is my own project. Every tool on this list has alternatives elsewhere; the client-side pattern is what I'm actually recommending.
1. JSON Formatter
Webhook debugging is where this earns its keep. Stripe hands you something like:
{"id":"evt_3PZk","type":"invoice.paid","data":{"object":{"amount_paid":4900,"customer":"cus_QRt8"}}}
Readable? Barely, and that's the short version. I paste it into fewly's JSON formatter, get proper indentation, and — the underrated part — validation for free, since the tool has to parse before it can pretty-print. Trailing comma in a hand-edited fixture file? It points at the line instead of letting me squint.
2. Text Diff
A feature worked on staging and 500'd in production. The entire diagnosis was two .env files pasted side by side: prod was missing REDIS_TLS=true and carried a stale API_BASE. Ninety seconds. No git, no vimdiff over SSH. Real code diffs still happen in the PR, obviously — this is for config-shaped text that never reaches version control: env files, nginx blocks, two versions of an email template. It also settles "did anything change on your side?" disputes with vendors, gently.
3. Hash Generator
Two habits. Checksums first: when a vendor publishes a SHA-256 next to their SDK download, I actually verify it now, because verifying costs ten seconds. Second, quick digests while sketching — hashing a canonical string to design a cache key or a dedupe ID. Yes, shasum -a 256 exists and I still use it in scripts. But when the string is already on my clipboard and a browser is already open, the tab wins on pure motion economics.
4. Timestamp Converter
1752868800 means nothing to me and never will. Logs speak epoch; incident reports speak "Friday around 9 p.m." A converter translates both directions and — the part I actually get wrong — handles timezones. When a user in Karachi reports something broke "last night," turning that into a UTC range I can grep is the real task, and doing offset math in my head at 1 a.m. has burned me more than once. The ISO 8601 output drops straight into API query params too, which ends the format guessing.
5. Cron Generator
I've written cron expressions for a decade and still don't fully trust myself with field order under pressure.
0 3 * * 1
Three a.m. every Monday. Or every March? Or the 1st of the month? (It's Monday. But you double-checked, didn't you.) A generator that renders the schedule back into plain English before it lands in a crontab has prevented at least two "why did this run 31 times" incidents that I know of.
6. Encoder / Decoder
OAuth debugging is nesting-doll decoding: a redirect_uri URL-encoded inside a query string, a base64 blob inside an Authorization header, occasionally both at once. Decode, read, fix, re-encode. If base64 still feels slightly mystical, MDN's glossary entry is the best ten-minute explanation I've found. After that, a paste box beats typing atob() into a console you don't have open.
7. YAML to JSON (and back)
GitHub Actions taught me that I cannot see YAML indentation errors after 6 p.m. A matrix build kept skipping one OS; the file looked fine. Converted to JSON, the bug was instant — my entry sat one level too high, a sibling of matrix instead of a child. YAML-to-JSON gives you the parser's-eye view, which is the view that matters. The reverse direction earns its spot whenever a machine-generated JSON config needs to become something humans can review without wincing. (The workflow syntax reference and I remain on speaking terms regardless.)
8. CSV Viewer
The 18 MB export problem: a spreadsheet app will open it, then immediately start improving it — dates reinterpreted for your locale, encodings guessed, columns reformatted. A read-only viewer does none of that. I skim, confirm the column names, spot-check that row 40,000 looks like row 4, close. Most of the time I never needed to edit the file. I needed to see it, and seeing shouldn't mutate.
9. Markdown and HTML, both directions
Release notes get written once, in Markdown. Then the email tool wants HTML, a CMS field wants Markdown back, and someone in marketing wants the announcement "as a web page." Round-tripping through a converter beats hand-repairing <li> soup in either direction. A recent favorite: a client sent brand copy as raw HTML scraped from their old site, and one paste turned it into Markdown I could commit to the project wiki. Small tool, weekly use, zero drama.
10. File Converter
The surprise entry. Product managers send specs as .docx; our docs live in the repo as Markdown. The file converter on the same hub does DOCX-to-Markdown in the tab — a 14-page spec becomes a reviewable pull request in about a minute, headings and lists intact. It goes the other way too, Markdown to PDF, for the people who want "a document" back.
Where the terminal still wins
None of this retires jq. Anything repeated, scheduled, or larger than ~50 MB belongs in a script, and jq's filter language is untouchable for surgical extraction mid-pipeline. The browser tools won a different niche: interactive, one-off, paste-shaped problems where startup cost dominates the actual work. Knowing which niche you're standing in is the skill.
The actual takeaway
My Homebrew list is a third of its former size and I haven't missed the utility folder once. The full set of tabs I use lives at fewly.tech/tools — 50-odd tools, free, client-side, no signup, and they work offline once loaded. But steal the pattern even if you skip the site: before trusting any "free online tool," open the Network tab and watch what leaves. If your data ships out for a task your laptop could do locally, find a better tab. My running total after four months: zero dollars, zero licenses, zero update prompts.
Suggested author bio: Moin is the founder of fewly, a free URL shortener with 50+ free browser-based tools. He builds the kind of small utilities he wishes came pre-installed.
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