Best IPA Signer for iPhone: Feather, Ksign, ESign, Scarlet

Every few weeks the same thread appears: apps that worked yesterday now throw “Unable to Verify App”, and the advice underneath it is a list of names — Feather, Ksign, ESign, Scarlet. They all do the same visible thing: sign an IPA on the phone and install it, no computer involved. What separates them is invisible and decides everything: whose certificate signs your apps. Get that part wrong and the tool barely matters, because the whole set dies in the same hour.

The 30-second answer

• Feather — open source, the most capable, and it signs nothing on its own: you bring the certificate.
• Ksign — a cleaner rebuild of ESign on top of Feather, popular because it ships with a shared certificate.
• ESign — the original was discontinued in 2025; what carries the name now is rebuilds and certificate sellers. Full breakdown: eSign on iOS 26.
• Scarlet — a store on a borrowed enterprise certificate, not a signer you control; it goes down with that certificate in every revoke wave. Full breakdown: Scarlet on iPhone.
• A managed service (this is what builds.io does) — a certificate scoped to your device, renewed for you, so there is nothing to import and nothing to re-sign.

Two kinds of signer, and the difference decides everything

A signer is only a wrapper around one step: it takes an IPA, applies a code-signing identity, and hands the result to iOS. The identity is the part that expires, gets revoked, or was never yours to begin with. Sort the tools by where that identity comes from and the confusion clears up:

You bring the certificate. Feather is the reference example. It is a signing app and nothing else — it will not give you an identity, so you supply one: a free Apple ID (7-day certificates, three apps), a paid Apple Developer account, or a certificate bought from a seller. The tool is stable because it has nothing to take away.

Somebody else brings the certificate. Scarlet and the current ESign builds work this way, and Ksign is the honest case of it — its own repository says it was built “specifically for Khoindvn to share his certificates, allowing more people to access sideloading without even having to buy a certificate.” One identity, shared by a crowd. Nothing to import, nothing to pay, and when Apple pulls that identity, everyone signed with it loses their apps at the same moment.

That second pattern is why revoke waves feel synchronised across the whole community — because they are. We covered the mechanics separately in why sideloaded apps get revoked.

Feather — the most capable, if you have an identity

Feather describes itself as a free on-device iOS/iPadOS application manager and installer that uses certificates from the Apple Developer Program. It is open source, keeps no analytics, reads AltStore repositories, and — the part advanced users care about — injects tweaks with Ellekit, supporting .deb and .dylib files. That last capability is why people who build their own modded apps stay with it.

The catch is in the wiki, which has separate pages for using an Apple Developer account, for a developer account without a Mac, and for certificates bought from KravaSign and Signulous. Read that as the honest system requirement: Feather assumes you have solved the certificate problem elsewhere. If you have not, it installs nothing.

Pick it if you have a paid developer account or a certificate you trust, and you want tweak injection with no strings attached.

Ksign — the ESign replacement, built on Feather

Ksign calls itself “the cleaner ESign app” and is a recreation of the discontinued one, built on Feather’s foundation. The interface is familiar to anyone coming from ESign, and it is open source too.

Its popularity, though, comes from the certificate that ships with it rather than the code — which puts it on the shared side of the line even though it is built from the same parts as Feather. That is a genuine convenience: sideloading with no purchase and no developer account. It is also the exact arrangement that ends abruptly. When the shared identity is revoked, the fix is not in the app — you wait for whoever maintains the certificate to publish another one.

Pick it if you want the ESign workflow back and you accept that continuity depends on someone else’s certificate.

ESign — the name outlived the app

ESign was the default answer to “how do I sign an IPA on my phone” for years. The original was discontinued in 2025 and its servers went dark; what circulates under that name today is a mix of community rebuilds and sites selling certificates with the ESign branding attached. The searches never stopped, so the name became a marketing asset — which is why “ESign Pro” and “lifetime ESign certificate” offers keep appearing, and why nobody can actually sell you a certificate Apple cannot revoke.

The mechanics of the app itself — the three places a certificate can come from, and what the DNS profile really does — are in eSign on iOS 26: how IPA signing actually works. The red flags before paying anyone are in iOS sideloading certificate scams.

Pick it if you already have a certificate and want the classic interface — otherwise Ksign is the maintained version of the same thing.

Scarlet — instant, on borrowed time

Scarlet is the odd one out here, because it is not really a signer you operate: it is a store that hands you apps already signed with an enterprise certificate someone else holds. Nothing to import, nothing to configure, apps in a minute. Apple revokes enterprise certificates precisely when they are used to distribute apps to large numbers of unaffiliated people — which is the entire premise — so a fresh one can last weeks or days depending on how visible it gets, and when it goes, Scarlet itself usually stops opening along with everything it installed.

Why the whole library dies at once, what “anti-revoke DNS” does and does not fix, and the specific catch for game mods: Scarlet on iPhone.

Pick it if you want an app installed in the next five minutes and genuinely do not mind rebuilding the setup later.

Why they all fail in the same week

When “Unable to Verify App” spreads across forums in a single day, it is rarely four separate bugs in four tools. It is one shared identity being pulled, and every app signed with it stopping at once. The tool you used only determines which certificate you were on.

The tell is simple: if reinstalling the signer fixes things for a few days, you are on a shared certificate. If nothing you do inside the app helps and you are waiting for an announcement, you are definitely on one. What that error means case by case — including the version where your own Apple ID is at fault — is in unable to verify app on iPhone.

One name that comes up in the same breath is not in this comparison for a reason: TrollStore never used certificates at all — it exploited a CoreTrust bug to install permanently signed apps, and Apple patched it in iOS 17.0.1. On anything newer there is no build, whatever the download sites imply (the version-by-version answer).

Free tools that sign with your own Apple ID (AltStore, SideStore, Sideloadly) avoid the shared-certificate failure entirely, and trade it for a different one: the 7-day refresh and the three-app limit. We ranked them by effort in every free way to sideload iPhone apps, and compared the big three head-to-head in AltStore vs SideStore vs LiveContainer.

Where a paid certificate fits

Buying a certificate — the KravaSign and Signulous route Feather documents — is the middle path: no weekly refresh, no shared-identity roulette, an identity that is at least nominally yours. It is a real option, and it has one structural weakness. You are trusting a seller to still be there after the next revoke, and the market has a long history of accounts that vanish and reappear under a new name. Never hand over an Apple ID password for one; a device UDID is all signing requires.

What managed signing changes

builds.io is the version where the certificate question is simply not yours. Signing is handled on our side, scoped to your device, and renewed without a refresh cycle — you install from the catalog in Safari, in one tap, with no p12 to import, no DNS profile, and no shared identity to go down with.

• No computer and no cable, ever.
• No 7-day refresh and no three-app limit — push notifications included.
• On Premium, revokes are covered: if a certificate goes down, a new one is issued and your apps come back. If Apple puts your account into an ineligible cooldown, the lost days are credited back.

It is a subscription, so it is not free — the honest trade is money for time. One expectation to set: when you first add a device, Apple processes it before apps go live. Most devices are ready within a day; some take up to three days. It is normal and it happens once.

What people install once signing stops being the problem

So which signer should you use?

If you already hold a developer account or a certificate you trust, Feather is the best tool of the four and it is not close — open source, tweak injection, no dependency on anyone else’s identity. If you want the ESign experience back for free, Ksign is the maintained version of it, with the shared-certificate caveat attached. Scarlet is for the five-minute install you are willing to lose. And the name ESign by itself is now mostly a signal that someone is selling you something.

If the part you actually want to stop dealing with is the certificate — not the app, not the interface, the certificate — then no signer solves it, because none of them own the problem. Browse the catalog at builds.io and install what you were signing manually, or use the free-tool ranking above to keep doing it yourself with your own Apple ID.