What is the bitmap in ISO 8583?

The bitmap is a 64-bit field where each set bit indicates that the corresponding data element is present. If bit 1 of the primary bitmap is set, a secondary bitmap follows, extending coverage to fields 65 through 128.

What is the processing code (DE 3) in ISO 8583?

Data element 3 is a six-digit processing code. The first two digits give the transaction type (for example 00 for a purchase of goods or services, 01 for a cash withdrawal, 20 for a refund, 30 for a balance inquiry), the next two give the from-account type and the last two the to-account type (for example 00 unspecified, 10 savings, 20 checking, 30 credit). Exact values vary by network and acquirer specification.

What does the response code in DE 39 mean?

Data element 39 carries the response code returned by the issuer or host. Common values are 00 approved, 05 do not honor, 14 invalid card number, 51 insufficient funds and 91 issuer or switch unavailable. Many networks add their own codes, so check the specification for your acquirer or network.

ISO 8583 Parser & Bitmap Decoder Online (Free)

ISO 8583 Decoder

edit_note By the Paying.co engineering team · Updated August 6, 2026

Paste an ISO 8583 message and read its Message Type Indicator, expand the primary and secondary bitmaps, and see exactly which data elements the message declares — each labeled by field name.

Quick answer

What is ISO 8583? ISO 8583 is the international standard for financial transaction messaging between cards, terminals, acquirers, and issuers. A message has a Message Type Indicator, one or two bitmaps marking which data elements are present, and the data elements themselves.

About ISO 8583

ISO 8583 is the messaging standard that moves an authorization, reversal, or settlement record between a terminal, an acquirer, a network, and an issuer. Every message opens with a four-character Message Type Indicator describing its version, class, function, and origin, followed by a bitmap that flags which of the 128 possible data elements are present, and then the data elements themselves in order.

Reading the bitmap

The primary bitmap is 64 bits covering fields 1 through 64
If field 1 is set, a secondary bitmap follows, covering fields 65 through 128
Each set bit means that data element is present in the message body

This decoder identifies the MTI, expands both bitmaps, and lists every present field with its standard name. Field value parsing depends on each acquirer's data-element format table, so values are not split here — the focus is structure and which elements are declared.

Frequently asked questions

What is the MTI?

The Message Type Indicator is the four-digit code at the start of the message — for example 0200 is an authorization request and 0210 its response.

Why only the field list, not field values?

Data-element formats vary by network and acquirer specification. The bitmap and field names are universal; reliably splitting values requires the specific format table.

Need a field and code reference?

See the ISO 8583 reference for MTI digits, common data elements, processing codes and response codes.

What is the processing code (DE 3)?

A six-digit field: the first two digits are the transaction type (00 purchase, 01 cash withdrawal, 20 refund, 30 balance inquiry), the next two the from-account type and the last two the to-account type (00 unspecified, 10 savings, 20 checking, 30 credit). Values vary by network and acquirer specification.

What does the response code (DE 39) mean?

It is the issuer or host answer: 00 approved, 05 do not honor, 14 invalid card number, 51 insufficient funds, 91 issuer or switch unavailable. Networks add their own codes, so confirm against your specification.

Going through EMV certification?

Host message formats are part of every EMV Level 3 project. See our EMV Level 3 certification services →

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We build and certify against acquirer and network specifications regularly. See platform integrations →