About these tools

Who makes this

Maris Stella Labs is a small open-source lab in Colorado, founded and run by Duncan Haywood. AI coding agents build the tools and the research in public, in one GitHub repository; every change is tested before it ships, and the history of every merge is public. Everything is MIT licensed, so you can use it, change it, or run your own copy as a business of your own.

What this is

A working set of 1321 small, single-purpose web tools across 15 areas — pricing a job, checking what a marketplace sale actually nets, planning cashflow, normalising freight quotes, and assembling the evidence a compliance obligation asks for. Each one exists because the arithmetic behind it is easy to get wrong under time pressure and expensive to get wrong in front of a customer.

They are deliberately narrow. A tool here answers one question for one kind of business, rather than being a spreadsheet template that answers none of them well.

What happens to what you type

The one thing that is counted is which tools get opened, as a plain tally that is written to your own browser's local storage. One page-view ping per load also goes to this site's own open-source counter: it carries the page's name and, when you arrived by one of this portfolio's own channel links (a ?ref= tag such as ?ref=npm, removed from the address bar on arrival), that channel's name, plus what kind of site sent you (a label from a fixed list, such as google, reddit or other, worked out in your browser so the referring address itself is never sent), and nothing else. From the request itself the counter also reads the country it came from (Cloudflare's two-letter code, such as US) and whether the browser string is a phone's, a tablet's or a desktop's. It keeps one number per page, per channel, per kind of site, per country and per device type, per day, and none of these is linked to another or to you. Self-declared crawlers are tallied separately by name (such as googlebot) and never counted as visits. No IP address, cookie, browser string or referring address is stored. The daily totals are committed to the public repository. That counter's host sees each request the way any web server does; the counter stores none of it. It exists so the next tool built is one people actually opened. Browsers sending Do Not Track or Global Privacy Control are not counted at all, and there is an opt-out checkbox at the foot of the tool list.

Why it is free

Because keeping it free costs almost nothing. A static page has no per-user cost, so there is no usage to meter and no reason to build a paywall around arithmetic. There is no paid tier, no trial, and no feature held back — the version you are using is the whole product.

If one of these has saved you money, sponsoring on GitHub or buying me a coffee is welcome and entirely optional. Declining changes nothing about what any tool does, and nothing here is gated behind it.

What these tools are not

They are estimates and working records, not professional advice and not a determination made on anyone's behalf. They do not replace a quantity surveyor, an accountant, a lawyer, or an engineer, and the output of any of them is a starting figure to check against your own numbers before you quote it to a customer or file it anywhere. The full terms are in the footer of this and every other page.

Linking to these tools

You do not need permission to link to anything here, quote a page, or screenshot a result — for a forum answer, a trade newsletter, a course handout, or a write-up. Linking straight to the individual tool is more use to a reader than linking to the front page. If it helps, here is the description, already written:

One line

1321 free, private calculators for small businesses — bid pricing, marketplace fees, cashflow and compliance checks. No account, everything runs in your browser.

A paragraph

Maris Stella Labs is a collection of 1321 free web tools for people who run a small business: trade contractors pricing a job, marketplace sellers working out what a sale actually nets, logistics buyers comparing quotes, and small teams assembling compliance evidence. Every tool is a single static page that does its arithmetic in the visitor's own browser. There is no account system, no payment, and no third-party analytics — the numbers a user types never leave their device, except on Does your pinned workflow load something unpinned underneath it?, AI Bookkeeper: double-entry books that learn from your corrections, ATS Resume Checker, Babysitting Business Kit: free, private, in your browser, CAA Record Checker, Cancel Flow, Changelog Keeper, Churn Radar, Cron Heartbeat, Deal Keeper, DNS Change Evidence, Drip Keeper, Dunning Engine, Email Authentication Checker (SPF, DKIM, DMARC, BIMI), Error Keeper, Feedback Board, Form Inbox, ICP Lens, Interview Content Studio: one interview, a month of content for every platform, License Keeper, Would a spend cap have stopped your runaway LLM bill?, Turn meeting notes into owned, dated action items, Meter Keeper, MRR Pulse, Simulate conversations between fictional personalities, PQL Radar, Price drop alerts for any shop, on your own GitHub, Proposal Maker, Which of your PyPI dependencies lack a provenance attestation?, Which federal contracts in my niche expire next?, Rev Rec, Review Reply Desk, RFP Compliance Matrix Generator, Sales Agent, Sales Cadence Builder, Sales Call Notes Desk, Shift Roster Builder, Sign Keeper, Slot Keeper, Sponsor Ready, status-keeper, Subdomain Takeover Checker, Support Agent, Support Desk, Survey Keeper, Testimonial Keeper, Trial Converter, Did an extension you already trust just change what it does?, Waitlist Keeper, and webhook-relay, where the one thing you paste — the lookup target — goes to the public API it checks (raw.githubusercontent.com, api.anthropic.com, api.openai.com, generativelanguage.googleapis.com, hcb.hackclub.com, localhost:11434, localhost:1234, localhost:8080, www.irs.gov, api.resend.com, api.stripe.com, api.twilio.com, x, cloudflare-dns.com, github.com, api.telegram.org, dns.google, dns.quad9.net:5053, api.postmarkapp.com, api.sendgrid.com, stripe.com, proxy.local, ntfy.sh, pypi.org, api.usaspending.gov, accounts.google.com, api.hubapi.com, api.pipedrive.com, login.microsoftonline.com, mail.google.com, oauth2.googleapis.com, marisstella.app, www.w3.org, api.github.com, and marketplace.visualstudio.com) and nowhere else, and each tool keeps working offline once it has been opened. All 1321 are free with no gated features and no paid tier.

The facts, if you would rather write your own

• 1321 tools across 15 categories, all free, none gated.
• Runs client-side. Static pages; no account, no third-party analytics; works offline once opened. Does your pinned workflow load something unpinned underneath it?, AI Bookkeeper: double-entry books that learn from your corrections, ATS Resume Checker — the copy-paste test, free, no sign-up, Babysitting Business Kit: free, private, in your browser, CAA Record Checker, Cancel Flow — save-offer cancellation flow for Stripe, self-hosted, Changelog Keeper — changelog page, feeds and a What's new widget, self-hosted, Churn Radar — see who is about to cancel before they do, Cron Heartbeat — dead man's switch for cron jobs, self-hosted, Deal Keeper — which deals are really at risk, and what will actually close, DNS Change Evidence — prove what a DNS change actually did, Drip Keeper — self-hosted lifecycle email, Dunning Engine — failed payment recovery for Stripe, self-hosted, Email Authentication Checker (SPF, DKIM, DMARC, BIMI), Error Keeper — know when your app breaks, on your own server, Feedback Board — a Canny alternative you host yourself, Form Inbox — a Formspree alternative you host yourself, ICP Lens — who do your best customers have in common, and who else looks like them?, Interview Content Studio: one interview, a month of content for every platform, License Keeper — license keys for Stripe sellers, self-hosted, Would a spend cap have stopped your runaway LLM bill?, Turn meeting notes into owned, dated action items, Meter Keeper — self-hosted usage metering for Stripe, MRR Pulse — Stripe MRR and churn dashboard, self-hosted, Simulate conversations between fictional personalities, PQL Radar — find the free signups about to become customers, Price drop alerts for any shop, on your own GitHub, Proposal Maker — free client proposal generator, no signup, Which of your PyPI dependencies lack a provenance attestation?, Which federal contracts in my niche expire next?, Rev Rec — Stripe deferred revenue schedule, self-hosted, Review Reply Desk — reply to every review in minutes, free and private, RFP Compliance Matrix Generator, Sales Agent — sort sales replies, update your list, approve the drafts, Sales Cadence Builder — a prospecting sequence for every lead, checked before you send, Sales Call Notes Desk — notes in, CRM fields and follow-up out, free and private, Shift Roster Builder — free, private, in your browser, Sign Keeper — self-hosted e-signature with a verifiable certificate, Slot Keeper — a booking page you host yourself, Sponsor Ready, status-keeper — your own status page, free, Subdomain Takeover Checker, Support Agent — AI customer service that knows when to hand off, Support Desk — a help desk you host yourself, Survey Keeper — an NPS survey that says why the score is what it is, Testimonial Keeper — collect testimonials and show a wall of love, self-hosted, Trial Converter — trial-to-paid conversion for Stripe, self-hosted, Did an extension you already trust just change what it does?, Waitlist Keeper — a self-hosted referral waitlist, and webhook-relay — keep webhooks safe while your app is down are the documented exceptions — see Privacy above.
• MIT licensed. Every tool ships its licence text alongside it — open any tool and add LICENSE to its address.
• Front page: https://marisstella.app/

Please do not describe these as certified, audited, guaranteed, or as professional advice — they are none of those things, and saying so would mislead the person you are recommending them to.

Embedding a tool on your own page

Every one of the 1321 tools here can be framed on someone else's page — a trade association's resource page, a supplier's blog post, a forum's sidebar. Open any tool and scroll to the bottom for a ready-made, copyable snippet built from that page's own address and title; there is nothing to write by hand. It always takes this shape:

<iframe src="https://marisstella.app/<tool-slug>/?pfEmbed=1" style="width:100%;max-width:820px;border:0;min-height:1400px" loading="lazy"></iframe>

• Same arithmetic, same disclaimer. The framed page is the calculator's own page, not a stripped-down copy, so it keeps the tool's full working and its liability notice.
• Links back. A framed tool swaps its own site-wide navigation for one line linking back to the full page here, so a visitor can always reach the rest of the site.
• Adds nothing. No script, cookie, or request is added by embedding — the framed page runs the same client-side arithmetic described above, on the host's page instead of this one.
• 1400px is a starting height, not a fit for every form; most hosts adjust it once the embed is on the page.

This needs no permission and no message to us first.

For crawlers and assistants

The catalogue is published in machine-readable form so an assistant can cite the right tool rather than guess at one: catalog.json lists every tool with its category and description, llms.txt is the same catalogue as prose, and sitemap.xml indexes every published page. Every tool page carries SoftwareApplication structured data. To follow new tools rather than re-read the catalogue, subscribe to the Atom feed.